Exploring the medicinal potential of secondary metabolites derived from selected medicinal plants of Ethiopia flora: an integrated study of antidiabetic, anticancer, antibacterial and antioxidant activities, phytochemical analysis, ADMET profiling, and molecular docking insights

Abstract

Since ancient time, human beings have utilized medicinal plants for a variety of purposes, such as food, flavors, cosmetics, clothing dying, and, most importantly, medicine to treat a wide range of diseases. In these studies, six medicinal plants; Crinum abyssinicum, Calotropis procera, Caylusea abyssinica, Justicia schimperiana, Verbascum sinaiticum, and Lagenaria abyssinica with a variety of traditional uses were selected. The air-dried powdered sample of the plant’s material was extracted successively with dichloromethane/methanol (1:1), and methanol by maceration. Fractionation of the extracts was carried out using silica gel column chromatography. Spectroscopic techniques such as 1H-NMR, 13C-NMR, DEPT-135, COSY, HSQC, and HMBC were used to elucidate the structures of isolated compounds. Essential oils were extracted by hydrodistillation method and their chemical analyses were performed by Gas chromatography coupled to mass spectrometry (GC-MS). The disc diffusion method was used to assess antibacterial activity against four bacterial species. Broth dilution method was also used to test antimicrobial activity against a set of microorganisms (bacterial and 3 fungal strains). The radical scavenging activity of the extracts and isolated compounds were evaluated using DPPH method. Antidiabetic potentials of the plant’s crude extracts were evaluated by α-amylase inhibition assay. The cytotoxicity effects of crude extracts were evaluated in vitro against MCF-7 human breast cancer cell lines by using MTT assay. The in vitro anti-Acanthamoeba activity of the extracts has been tested against Acanthamoeba triaugularis and castellanii using micro dilution method. The MDCK cell line and the MTT method were used to examine the extracts' anti-influenza A virus activities. The molecular docking analysis of the isolated compounds was conducted using AutoDock vina 4.2 open-source program. ADMET was predicted by SwissADME and PreADMET property predictions. Silica gel column chromatographic separation of the extracts of six selected medicinal plants afforded thirty-seven known compounds identified by comprehensive analyses of NMR data and comparison with literature data. The class of compounds obtained were identified as fatty acids, fatty acid esters, steroids, ursane-type triterpenoids, flavonoids, stilbenoids and iridoid phenylethanoid glycosides of which 32 compounds were reported herein for the first time from the studied medicinal plants. The essential oils obtained from the bulb of C. abyssinicum, leaves, and roots of J. schimperiana, leaves, flowers, and seeds of C. procera, roots, and seeds of L. abyssinica, leaves, roots of V. siniaticum, and aerial parts of C. abyssinica were analyzed by GC-MS. The GC-MS analysis of essential oils revealed a total of 62, 52, 54, 59, 46, 45, 35, 41, 61, 32, and 41 chemical constituents, representing 100, 99.73, 98.84, 99.45, 99.34, 100, 100, 99.78, 99.8, 100, and 99.78 % of the total oil contents, respectively. The MeOH and CH2Cl2/MeOH (1:1) root extract of C. abyssinicum had strong activity against P. aeruginosa and S. aureus with a maximum zone of inhibition of 16.3  0.3 mm and 16.7  1.2 mm at 250 µg/ml, respectively. Methanolic extract of J. Schimperiana and C. abyssinica had the maximum zone of inhibition of 17.0  0.3 mm and 15.4  0.3 against E. coli., respectively. Among the plants tested, the methanolic extract of C. abyssinica (with the highest zone of inhibition of 18.3  0.4 mm against S. aureus) was very promising and showed significant inhibition of all tested bacterial pathogens. For J. schimperiana extracts, the smallest MIC value was recorded for the dichloromethane: methanol (1:1) extract against S. aureus, and E. faecalis which was 4.0 mg/mL. The DCM: MeOH (1:1), and MeOH extracts of V. sinaiticum roots showed the highest activity against S. epidermids with MIC value of 0.25 mg/mL. For isolated compounds, the XXIIIhighest mean inhibitory value was recorded by 231 (17.7  0.8) followed by 232 (17.0  1.2), 87 (14.3  0.5), 97 (13.9  0.2 mm), and 234 (12.7  0.4 mm), against E. coli at 500 μg/mL compared with ciprofloxacin (29.7  0.3) with similar concentration. Compound 79 displayed promising activity against S. aureus (14.1 ± 1.0 mm) at 500 μg/mL compared with Gentamycin (19.3 ± 0.5 mm). The S. aureus and S. agalactiae were highly susceptible to compound 246 with a MIC value of 0.25 mg/mL followed by compounds 242, and 243 with MIC values of 0.5 mg/mL against S. agalactiae. The strongest antibacterial effects were demonstrated with S. epidermidis, which exhibited a 0.0625 mg/mL MIC for compound 247, followed by compounds 248, 249, and 250 against S. aureus, S. typhimurium, and S. epidermidis with a MIC value of 0.5 mg/mL for each, respectively, from V. sinaiticum. The DCM: MeOH (1:1) extract of C. abyssinicum (IC50 value 12.8 μg/mL) and C. abyssinica (IC50 value 12.5 μg/mL), MeOH extract of C. Procera (IC50 value 15.3 μg/mL), J. Schimperiana (IC50 value 10.8 μg/mL), and C. abyssinica (IC50 value 12.6 μg/mL) showed good antioxidant potential compared to ascorbic acid (IC50 value 3.1 μg/mL), and for isolated compounds, the results showed that, compounds 226 (70.8  0.2, IC50 = 10.20 g/mL), and 228 (79.6  0.6, IC50 = 0.60 g/mL) showed promising antioxidant potential. In comparison to ascorbic acid (88.1%) at a concentration of 200 g/mL, compounds 97 and 234 reduced the stable DPPH radical by 63.5% and 75.0%, respectively, indicating potential radical scavengers. Better anti- DPPH action was demonstrated by bis(2-ethylheptyl) phthalate (239) at a concentration of 200 g/mL with an IC50 value of 10.2 g/mL (70.8  0.2). In comparison to ascorbic acid (89.9%, IC50 = 1.3), compounds 245 (73.3%), 246 (77.9%), 249 (72.7%, IC50 =3.8), 250 (74.8%, IC50 = 4.2), 251(72.8%, IC50 =3.6), 252(73.2%, IC50 =3.38), 253 (71.1%, IC50 = 4.2), and 248 (70.7%, IC50 =4.7), displayed the highest radical scavenging activity. The in vitro antidiabetic activity results showed, the methanol roots extracts of C. abyssinica, and DCM/MeOH (1:1) leaves extract of J. schimperiana exhibited strong α-amylase enzyme inhibition with IC50 values of 7.8, and 7.5 mg/mL, respectively, at a concentration of 10.0 mg/mL compared to the positive control acarbose (IC50 = 4.4 mg/mL). Of all the studied plants, the DCM/MeOH (1:1) root extract of C. procera had the highest cytotoxic effect on the MCF-7 breast cancer cell line with 4.1% viability. The In vitro anti-Acanthamoeba activity of the extracts showed the dichloromethane: methanol (1:1) root extracts of V. sinaiticum showed a good inhibitory activity (% viability < 10) at 2 mg/mL against Acanthamoeba castellanii ATCC50739. The study of the antiviral activities of the DCM: MeOH (1:1) leaves extract of J. schimperiana displayed more effective at inhibiting A/H1N1/. The results of the molecular docking analysis for compounds revealed minimal binding energies of -5.0 to–8.9, -5.6 to–10.1, - 4.3 to -10.8, -5.1 to -11.0, -5.0 to -10.5, -4.5 to -9.9 kcal/mol against DNA gyrase B (PDB ID:7P2W), S. aureus Gyrase (PDB ID: 2XCT), human myeloperoxidase (PDB ID: 1DNU), PqsA (PDB ID 5OE3and human topoisomerase IIα (PDB ID: 4fm9), respectively. Of the tested isolated compounds, 226, 227, 231, 238, 241, 242, and 243 obeyed Lipinski’s rule of five with zero violations. The in vitro antibacterial, antioxidant, antidiabetic activity and molecular modeling analysis suggest the potential use of the isolated compounds and crude extracts as medicine which corroborate the traditional uses of the studied plants.