Studies on Chemical Constituents and Biological Activity of Abrus precatorius and Morinda elliptica

Wakawa, Henry Yusufu (2019) Studies on Chemical Constituents and Biological Activity of Abrus precatorius and Morinda elliptica. PhD thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

Chemical compounds were isolated from the leaves and root extracts of Abrus precarious and from the leaves and root bark of Morinda elliptica. Compounds isolated include 5,7-dimethoxyflavanone (96), xanthoxylin (97) and hexadecanoic acid (98) from the root extract of A. precatorius; beta-eudesmol (99) and squalene (100) from the leaf extract of A. precatorius; 2-hydroxy-1-methoxyanthracene-9,10-quinone (101), dehydroabietic acid (102), 3-(4-ethoxy-3-methoxyphenyl)-1-phenylprop-2-en-1-one (103) and benzaldehyde (104) from root bark extract of M. elliptica, and methyl cinnamate (105) from the crude leaf extract of M. elliptica. Cytotoxicity study was conducted to test for in-vivo Brine Shrimp Lethality Assay (BSLA) in terms of LC50. The results showed that dichloromethane and hexane fractions of A. precarious leaves extracts were more potent against the brine shrimp with LC50 values of 19.135 μg/mL and 32.627 μg/mL, respectively, while the similar fractions of the root extract showed LC50 of 14.951 μg/mL and 7.870 μg/mL, respectively. M. elliptica root extract showed that methanol and hexane fractions were more potent with LC50 values of 39.259 μg/mL and 58.483 μg/mL, respectively, while similar fractions of the leaves extract showed LC50 of 36.069 μg/mL and 35.483 μg/mL, respectively. Free radical scavenging activity of the extracts was tested using 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical at 517 nm against a standard antioxidant ascorbic acid which showed an EC50 value of 63.41 + 0.101 μg/mL. The leaf extract of A. precatorius revealed that methanol and dichloromethane fractions exhibited strong antioxidant activities with EC50 values of 35.33 + 0.210 μg/mL and 51.91 + 0.921 μg/mL, respectively, while the root extract showed dichloromethane and hexane fractions exhibited EC50 of 48.16 + 0.191 μg/mL and 50.18 + 0.122 μg/mL, respectively. The results of M. elliptica revealed that dichloromethane and methanol fractions of the leaf extracts showed strong antioxidant activities with EC50 values of 35.60 + 1.90 μg/mL and 86.00 + 2.10 μg/mL, respectively, while similar fractions of the root extract showed EC50 of 52.08 + 1.50 μg/mL and 42.70 + 1.50 μg/mL, respectively. Antibacterial potential was evaluated using Agar disc diffusion method by determining the zone of growth inhibition against selected human pathogenic bacteria (Staphylococcus aureus, Escherichia coli and Salmonella typhii) and was compared with that of standard drug chloramphenicol and DMSO expressed at p<0.05. Leaf extract of A. precatorius was observed to exhibit bactericidal activity at 500 µg/mL against S. typhii in hexane extract and S. aureus in methanol extract with mean values of 12.000 + 0.00 mm and 12.333 + 0.577 mm, respectively. The antifungal activity was determined against Aspergillus niger and Aspergillus flavus and compared with a standard antibiotic nystatin and DMSO at 500 μg/mL. The result showed leaf and root extracts of A. precatorius exhibited a significant activity against the test organisms. M. elliptica leaf and root extract showed significant activity against A. niger. Antidiabetic study of the crude leaves of A. precatorius was performed by assessing the hypoglycemic potential and effect on some biochemical and hematological parameters in normal and alloxan-induced diabetic albino rats. Diabetes was induced by a single dose of intraperitoneal injection of 150 mg/kg bwt of alloxan and a daily oral administration of different concentrations of extract (100, 200 and 400 mg/kg bwt) was done for 21 days and the result was determined at p<0.05. A significant decrease was observed in blood glucose, marker enzymes and hematological parameters in the diabetic treated rats. Compounds 96, 97, 101, 102, 104 and 105 were isolated for the first time. The dichloromethane leaf extract of M. elliptica was found to contain active phytochemical and the leaf extract of A. precatorius was found to contain hypoglycemic property. Keywords: Abrus precatorius, Morinda elliptica, secondary metabolites, antimicrobial activity, antioxidant activity, brine shrimp, diabetes, liver marker enzymes.

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