Isolation and structure elucidation of bioactive chemical constituents from Vitex pinnata, Artocarpus nobilis, Barleria prionitis, Buxus natalensis and Coprinus micaceus

This thesis describes phytochemical studies on four medicinally important plants, Vitex pinnata, Artocarpus nobilis, Barleria prionitis, Buxus natalensis and one saprophytic fungus, Coprinus micaceus . These findings are summarized as follows: 1. Chemical studies on the crude methanolic extract of Vitex pinnata yielded one new iridoid glucoside, 6"-glucosepedunculariside (88) and three known natural products, pedunculariside (89), agnuside ( 90) and p-hydroxy benzoic acid (91). Compounds 88-91 were found to exhibit weak to moderate GST/AChE inhibitory activities and antioxidant activity. 2. Phytochemical investigations on the crude ethanolic extract of Artocarpus nobilis resulted in the isolation of two new triterpenoids, [artocarpurate A (109), atocarpurate B (110)] four known triterpenoids, [cyclolaudenyl acetate (111), lupeol acetate (112), beta-amyrine acetate (113), 12,13-dihydromicromeric acid (114)] and two known flavonoids [artonins E (115) and artobiloxanthone (116)]. All of these compounds exhibited different levels of anti-AChE and anti-GST properties. Compounds 115 and 116 were found to be more potent GST inhibitors than the standard GST inhibitor sodium taurocholate whereas compound 113 showed good AChE inhibitory activitity (IC50 = 11.5 +/- 2.58). 3. Our studies on the crude ethanolic extract of aerial parts of Barleria prionitis afforded five known natural products, 8-O-acetylshanzhiside methyl ester (127), shanzhiside methyl ester (128), lupeol (129), betulinic acid (130) and pipataline (131). Pipataline was isolated in enough quantity to prepare three different analogues of this natural product by doing reactions on C-7/C-8 double bond and evaluate them for the aforementioned bioactivities. We were interested to see the role of this double bond in the moderate bioactivity of this compound. In this study, we discovered that by the addition of an amino group at C-7 position, acetylcholinesterase inhibitory activity was improved from IC50 value of 135.09 +/- 0.501 muM to 36.75 +/- 0.272muM. 4. Phytochemical studies on Buxus natalensis have resulted in the isolation of one new steroidal alkaloid, natalensamine-A (156). Compound 156 showed weak AChE inhibitory activity. 5. Chemical studies on the methanolic extract of Coprinus micaceus yielded two compounds, micaceol (179) and (Z, Z)-4-oxo-2, 5-heptadienedioic acid (180). Compound 179 was found to be new while 180 was isolated for the first time as a natural product. Compound 179 showed weak antibacterial activity against Staphylococcus aureus and Corynebacterium xerosis while compound 180 was inactive in this bioassay. Compound 180 showed weak GST inhibitory activity while compound 179 was inactive in this bioassay.