Synthesis, antioxidant, antiproliferative activity, molecular docking and DFT studies of novel isoxazole derivatives of diosgenin, a steroidal sapogenin from Dioscorea deltoidea.

Diosgenin [25R-spirost-5-en-3ß-ol], isolated from Dioscorea deltoidea was used as a starting material for synthesizing its various isoxazole derivatives. A library of fifteen isoxazole analogues (DG1-DG15) were synthesised via modification at the C-3 hydroxyl group. The resulting analogues were fully characterized by spectral techniques and evaluated for their antioxidant and anticancer activity against four breast cancer cell lines; MDA-MB-231, MDA-MB-468, MCF-7, and 4 T1, using MTT assay. Molecular docking studies were carried out for all analogues with EGFR protein (PDB id: 6LUD) to check their activity by inhibiting EGFR protein, which is an effective strategy for cancer cell death. Furthermore, DFT studies were carried out for four analogues. Among all analogues, compound DG6 and DG9 showed the highest scavenging activity and compound DG9 exhibited a maximum cytotoxic effect on the MDA-MB-468 and MCF-7 cell lines with an IC50 value of 6.25 µg/mL and 6.81 µg/mL, while compound DG5 was the least potent (IC50 25.89 µg/mL). Molecular docking results revealed that DG8 and DG9 afforded the highest binding energy of -14.33 and - 14.71 kcal/mol, respectively for the target EGFR protein. These results demonstrate the potential of diosgenin analogues as drug candidates for breast cancer therapy. Furthermore, DFT studies revealed that the molecules are more polarizable and have smaller energy gap between their HOMO and LUMO orbitals, the smallest being of DG9 (3.221 eV) and hence are more reactive.

Isolation, cytotoxicity evaluation and HPLC-quantification of the chemical constituents from Prangos pabularia.

Phytochemical analysis of the dichloromethane:methanol (1:1) extract of root parts of Prangos pabularia led to the isolation of twelve cytotoxic constituents, viz., 6-hydroxycoumarin (1), 7-hydroxycoumarin (2), heraclenol-glycoside (3), xanthotoxol (4), heraclenol (5), oxypeucedanin hydrate (6), 8-((3,3-dimethyloxiran-2-yl)methyl)-7-methoxy-2H-chromen-2-one (7), oxypeucedanin hydrate monoacetate (8), xanthotoxin (9), 4-((2-hydroxy-3-methylbut-3-en-1-yl)oxy)-7H-furo[3,2-g]chromen-7-one (10), imperatorin (11) and osthol (12). The isolates were identified using spectral techniques in the light of literature. 3-(4,5-dimethyl thiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity screening of the isolated constituents was carried out against six human cancer cell lines including lung (A549 and NCI-H322), epidermoid carcinoma (A431), melanoma (A375), prostate (PC-3) and Colon (HCT-116) cell lines. Osthol (12) exhibited the highest cytotoxicity with IC50 values of 3.2, 6.2, 10.9, 14.5, 24.8, and 30.2 µM against epidermoid carcinoma (A431), melanoma (A375), lung (NCI-H322), lung (A549), prostate (PC-3) and colon (HCT-116) cell lines respectively. Epidermoid carcinoma cell line A431 was sensitive to most of the compounds followed by lung (A549) cancer cell line. Finally a simple and reliable HPLC method was developed (RP-HPLC-DAD) and validated for the simultaneous quantification of these cytotoxic constituents in Prangos pabularia. The extract was analyzed using a reversed-phase Agilent ZORBAX eclipse plus column C18 (4.6×250 mm, 5 µm) at 250 nm wavelength using a gradient water-methanol solvent system at a flow rate of 0.8 ml/min. The RP-HPLC method is validated in terms of recovery, linearity, accuracy and precision (intra and inter-day validation). This method, because of shorter analysis time, makes it valuable for the commercial quality control of Prangos pabularia extracts and its future pharmaceutical preparations.