C. opaca leaves were collected in March 2011 from the Quaid-i-Azam University Islamabad, Pakistan, recognized by their local names and validated by Dr. Mir Ajab Khan, Department of Plant Sciences, Quaid-i-Azam University, Islamabad. A voucher specimen was deposited at the Herbarium of Pakistan Quaid-i-Azam University, Islamabad Pakistan for future reference.
The collected plant leaves were cleaned and dried under shade for fifteen days. Willy Mill of 60-mesh size was used to prepare powder of dried samples and then 5 kg powdered plant sample was extracted twice with 10 L of 95% methanol at 25°C for 48 h. For filtration Whatman No. 1 filter paper was used and then filtrate was concentrated on rotary evaporator (Panchun Scientific Co., Kaohsiung, Taiwan) under reduced pressure at 40°C and dry extract was stored at 4°C for further in vivo investigation.
High performance liquid chromatogrhy (HPLC)
50 mg of fine powder was extracted with 6 ml of 25% hydrochloric acid and 20 ml methanol for 1 h. The obtained extract was filtered to a volumetric flask and diluted to 100 ml with methanol. 10 μl was injected into HPLC column (20RBAX ECLIPSE, XDB-C18, 5 μm; 4.6 × 150 mm, Agilent USA) with UV–VIS Spectra-Focus detector, injector-auto sampler. Solvent A (0.05% trifluoroacetic acid) and solvent B (0.038% trifluoroacetic acid in 83% acetonitrile (v/v) with the following gradient: 0–5 min, 15% B in A, 5–10 min, 70% B in A, 10–15 min, 70% B in A. The flow rate was 1 ml/min and injection volume was 10 μl. Various standard compounds including rutin, myricetin, vitexin, orientin, hyperoside, isovitexin, isoquercetin, luteolin, apigenin, kaempherol, and luteolin-7-glucoside were run for comparative detection and optimized. The calibration curves were defined for each compound in the range of sample quantity 0.02-0.5 μg. All samples were assayed in triplicate.
Six-week-old male Sprague Dawley rats weighing 180 ± 10 g were provided with food and water ad libitum and kept at 20–22°C on a 12-h light–dark cycle. All experimental procedures involving animals were conducted in accordance with the guidelines of National Institutes of Health (NIH guidelines). The study protocol were approved by Ethical committee of Quaid-i-Azam University Islamabad. The rats were acclimatized to laboratory condition for 7 days before commencement of experiment. For chronic toxicity eight week experiment was designed. 42 male albino rats were randomly divided into seven groups (6 rats of each group). Administration of CCl4 (0.5 ml/kg b.w., 20% CCl4/olive oil) was intraperitoneally (i.p.) twice a week for eight weeks. At the same time, the rats were administered individually silymarin (50 mg/kg b.w.) and extract (100, 200 mg/kg b.w.) orally twice a week for eight weeks.
Following dosing plan was adapted for the study.
Group I: the normal control received only feed
Group II: Olive oil (0.5 ml/kg b.w., i.p.) + DMSO (0.5 ml/kg b.w. orally)
Group III: CCl4 twice a week (0.5 ml/kg b.w., i.p., 20% CCl4/olive oil)
Group IV: CCl4 twice a week (0.5 ml/kg b.w., i.p.) + sylimarin (50 mg/kg b.w., orally)
Group V: CCl4 twice a week (0.5 ml/kg b.w., i.p.) + MLC (100 mg/kg b.w., orally)
Group VI: CCl4 twice a week (0.5 ml/kg b.w., i.p.) + MLC (200 mg/kg b.w., orally)
At the end of eight weeks, after 24 h of the last treatment, Urine was collected and stored at −70°C for further analysis, and then animals were given chloroform anesthesia and dissected from ventral side. All the animals were sacrificed; blood was drawn prior to the excision of organ tissues. The serum was stored at −80°C after separation until it was assayed as described below. After taking blood the testis were removed and washed in ice cold saline. Subsequently, half of the organs were treated with liquid nitrogen and stored at −80°C for further enzymatic and DNA damage analysis while the other portion was processed for histology.
Assesment of reproductive hormones and lipid profile of serum
Serum analysis of testicular hormones like FSH, LH, testosterone, prolactin and esteradiol were radioimmunoassayed by using Marseille Cedax 9 France Kits and Czch Republic Kits from Immunotech Company. Then again, lipid profile such as Triglycerides, total cholesterol, LDL and LDH waere estimated by using standard AMP diagnostic kits (Stattogger Strasse 31b 8045 Graz, Austria).
Assessment of antioxidant enzymes
10% homogenate of tissue was prepared in 100 mM KH2PO4 buffer containing 1 mM EDTA (pH 7.4) and centrifuged at 12,000 × g for 30 min at 4°C. The supernatant was collected and used for the following parameters as described below.
Catalase assay (CAT)
CAT activities were determined by the method of Chance and Maehly  with some modifications. The reaction solution of CAT activities contained: 2.5 ml of 50 mM phosphate buffer (pH 5.0), 0.4 ml of 5.9 mM H2O2 and 0.1 ml enzyme extract. Changes in absorbance of the reaction solution at 240 nm were determined after one minute. One unit of CAT activity was defined as an absorbance change of 0.01 as units/min.
Peroxidase assay (POD)
Activities of POD were determined by the method of Chance and Maehly  with some modifications. The POD reaction solution contained: 2.5 ml of 50 mM phosphate buffer (pH 5.0), 0.1 ml of 20 mM guaiacol, 0.3 ml of 40 mM H2O2 and 0.1 ml enzyme extract. Changes in absorbance of the reaction solution at 470 nm were determined after one minute. One unit of POD activity was defined as an absorbance change of 0.01 units/min.
Superoxide dismutase assay (SOD)
SOD activity was estimated by the method of Kakkar et al. . Reaction mixture of this method contained: 0.1 ml of phenazine methosulphate (186 μM), 1.2 ml of sodium pyrophosphate buffer (0.052 mM; pH 7.0), 0.3 ml of supernatant after centrifugation (1500 × g for 10 min followed by 10000 × g for 15 min) of testis homogenate was added to the reaction mixture. Enzyme reaction was initiated by adding 0.2 ml of NADH (780 μM) and stopped after 1 min by adding 1 ml of glacial acetic acid. Amount of chromogen formed was measured by recording color intensity at 560 nm. Results are expressed in units/mg protein.
Glutathione-S-transferase assay (GST)
Glutathione-S-transferase activity was assayed by the method of Habig et al. . The reaction mixture consisted of 1.475 ml phosphate buffer (0.1 mol, pH 6.5), 0.2 ml reduced glutathione (1 mM), 0.025 ml (CDNB) (1 mM) and 0.3 ml of homogenate in a total volume of 2.0 ml. The changes in the absorbance were recorded at 340 nm and enzymes activity was calculated as nM CDNB conjugate formed/min/mg protein using a molar extinction coefficient of 9.6 × 103 M-1cm-1.
Glutathione reductase assay (GR)
Glutathione reductase activity was determined by method of Carlberg and Mannervik . The reaction mixture consisted of 1.65 ml phosphate buffer: (0.1 mol; pH 7.6), 0.1 ml EDTA (0.5 mM), 0.05 ml oxidized glutathione (1 mM), 0.1 ml NADPH (0.1 mmol) and 0.1 ml of homogenate in a total volume of 2 ml. Enzyme activity was quantitated at 25°C by measuring disappearance of NADPH at 340 nm and was calculated as nM NADPH oxidized/min/mg protein using molar extinction coefficient of 6.22 × 103 M-1cm-1.
Glutathione peroxidase assay (GPx)
Glutathione peroxidase activity was assayed by the method of Mohandas et al. . The reaction mixture consisted of 1.49 ml phosphate buffer (0.1 M; pH 7.4), 0.1 ml EDTA (1 mM), 0.1 ml sodium azide (1 mM), 0.05 ml glutathione reductase (1 IU/ml), 0.05 ml GSH (1 mM), 0.1 ml NADPH (0.2 mM), 0.01 ml H2O2 (0.25 mM) and 0.1 ml of homogenate in a total volume of 2 ml. The disappearance of NADPH at 340 nm was recorded at 25°C. Enzyme activity was calculated as nM NADPH oxidized/min/mg protein using molar extinction coefficient of 6.22 × 103 M-1cm-1.
Quinone reductase assay (QR)
The activity of quinone reductase was determined by the method of Benson et al. . The 3.0 ml reaction mixture consisted of 2.13 ml Tris–HCl buffer (25 mM; pH 7.4), 0.7 ml BSA, 0.1 ml FAD, 0.02 ml NADPH (0.1 mM), and 0.l ml of homogenate. The reduction of dichlorophenolindophenol (DCPIP) was recorded at 600 nm and enzyme activity was calculated as nM of DCPIP reduced/min/mg protein using molar extinction coefficient of 2.1 × 104 M-1cm-1.
Reduced glutathione assay (GSH)
Reduced glutathione was estimated by the method of Jollow et al. . 1.0 ml sample of homogenate was precipitated with 1.0 ml of (4%) sulfosalicylic acid. The samples were kept at 4°C for 1 h and then centrifuged at 1200 × g for 20 min at 4°C. The total volume of 3.0 ml assay mixture contained 0.1 ml filtered aliquot, 2.7 ml phosphate buffer (0.1 M; pH 7.4) and 0.2 ml DTNB (100 mM). The yellow color developed was read immediately at 412 nm on a SmartSpecTM plus Spectrophotometer. It was expressed as μM GSH/g tissue.
Estimation of lipid peroxidation assay (TBARS/LPO)
The assay for lipid peroxidation was carried out following the modified method of Iqbal et al. . The reaction mixture in a total volume of 1.0 ml contained 0.58 ml phosphate buffer (0.1 M; pH 7.4), 0.2 ml homogenate sample, 0.2 ml ascorbic acid (100 mM), and 0.02 ml ferric chloride (100 mM). The reaction mixture was incubated at 37°C in a shaking water bath for 1 h. The reaction was stopped by addition of 1.0 ml 10% trichloroacetic acid. Following addition of 1.0 ml 0.67% thiobarbituric acid, all the tubes were placed in boiling water bath for 20 min and then shifted to crushed ice-bath before centrifuging at 2500 × g for 10 min. The amount of TBARS formed in each of the samples was assessed by measuring optical density of the supernatant at 535 nm using spectrophotometer against a reagent blank. The results were expressed as nM TBARS/min/mg tissue at 37°C using molar extinction coefficient of 1.56 × 105 M-1cm-1.
Hydrogen peroxide assay (H2O2)
Hydrogen peroxide (H2O2) was assayed by H2O2-mediated horseradish peroxidase-dependent oxidation of phenol red by the method of Pick and Keisari . 2.0 ml of homogenate sample was suspended in 1.0 ml of solution containing phenol red (0.28 nM), horse radish peroxidase (8.5 units), dextrose (5.5 nM) and phosphate buffer (0.05 M; pH 7.0) and were incubated at 37°C for 60 min. The reaction was stopped by the addition of 0.01 ml of NaOH (10 N) and then centrifuged at 800 × g for 5 min. The absorbance of the supernatant was recorded at 610 nm against a reagent blank. The quantity of H2O2 produced was expressed as nM H2O2/min/mg tissue based on the standard curve of H2O2 oxidized phenol red.
DNA had been isolated and its fragmentation percent was quantified in molecular studies of in vivo toxicity.
DNA fragmentation assay with diphenylamine reaction
DNA fragmentation from tissue extract was determined using the procedure of Wu et al. . 100 mg tissue was homogenized in TTE solution. 0.1 ml of homogenate was labeled B, centrifuged at 200 × g at 4°C for 10 min, got supernatant labeled S. S tubes were centrifuged at 20,000 × g for 10 min at 4°C to separate intact chromatin, was labeled T. 1.0 ml of 25% TCA was added in all tubes T, B, S and incubated over night at 4°C. After incubation precipitated DNA was recovered by pelleting for 10 min at 18,000 × g at 4°C. 160 μl of 5% TCA was added to each pellet and heated for 15 min at 90°C then 320 μl of freshly prepared DPA solution was added, vortexed and incubated for 4 hr 37°C. Optical density was read at 600 nm with a spectrophotometer (Smart spec™ Plus, catalog # 170–2525).
DNA Isolations and ladder assay
DNA was isolated by using the methods of Wu et al.. 100 mg of tissue in a petri dish was washed with DNA Buffer and homogenized in 1 ml lysis buffer. 100 μl of proteinase K (10 mg/ml) and 240 μl 10% SDS, shaked gently, and incubate overnight at 45°C in a water bath then 0.4 ml of phenol, was added shaked for 5–10 min, and centrifuge at 3000 rpm for 5 min at 10°C. Supernatant was mixed with 1.2 ml phenol, 1.2 ml Chloroform/isoamyl alcohol (24:1); shaked for 5–10 min, and centrifuged at 3000 rpm for 5 min at 10°C. 25 μl of 3 M sodium acetate (pH 5.2) and 5 ml ethanol was added with supernatant, shake until DNA was precipitated. DNA was washed with 70% ethanol, dried, dissolved in TE buffer and its concentration checked at 260 and 280 nm. 5 μg of total DNA and 0.5 μg DNA standard per well were loaded on 1.5% agarose gel containing ethidium bromide. Electrophoresis was performed for 45 min with 100 V batteries, and DNA was observed under digital gel doc system and photographed.
Histopathological study of tissue
After weighting the portion specifies for histology small pieces of each tissue was fixed for 3–4 h in fixative sera followed by dehydration with ascending grades of alcohol (80%, 90%, and 100%) and transferred in cedar wood oil. When tissue becomes clear then all tissues were embedded in paraplast and prepared blocks for further microtomy. 3–4 μm thin slides were prepared with microtome; wax was removed, stained with hemotoxilin-eosin and photographed under light microscope at 10x and 40x.
To find the different treatment effects of in vivo studies one way analysis of variance was carried by computer software SPSS 13.0. Level of significance among the various treatments was determined by LSD at 0.05% level of probability.