METHODS AND RESULTS: In our work, 10 naturally occurring phenolic compounds were evaluated for their inhibitory potential towards the lignolytic enzymes of G. boninense. Additionally, the lignin-degrading enzymes were characterized. Most of the peholic compounds exhibited an uncompetitive inhibition towards the lignin-degrading enzymes. Benzoic acid was the superior inhibitor to the production of lignin-degrading enzymes, when compared between the 10 phenolic compounds. The inhibitory potential of the phenolic compounds towards the lignin-degrading enzymes are higher than that of the conventional metal ion inhibitor. The lignin-degrading enzymes were stable in a wide range of pH but were sensitive to higher temperature.
CONCLUSION: The study demonstrated the inhibitor potential of 10 naturally occurring phenolic compounds towards the lignin-degrading enzymes of G. boninense with different efficacies.
SIGNIFICANCE AND IMPACT OF THE STUDY: The study has shed a light towards a new management strategy to control basal stem rot disease in oil palm. It serves as a replacement for the existing chemical control.
OBJECTIVES: This study aimed to evaluate the antihyperlipidemic effect, antioxidant potential and cytotoxicity of aqueous and methanolic extracts of ripe and unripe fruits, leaves and stem of A. carambola.
METHODS: Antihyperlipidemic activity was assessed in poloxamer-407 (P-407) induced acute hyperlipidemic rat's model. The antioxidant activity was assessed in vitro using 2, 2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging, 1-diphenyl-2-dipicrylhydrazyl radical scavenging (DPPH) and ferric reducing antioxidant power (FRAP) assays. In addition, cytotoxicity of A. carambola extracts was assessed using MTS assay on four leukemic cell lines (human colon cancer, human promyeloid leukemia, erythroid leukemia, acute myeloid leukemia) and one normal cell (human umbilical vein endothelial cells).
RESULTS: Methanolic extract of leaves had the most potent antihyperlipidemic activity in P-407 model, whereby it significantly reduced serum levels of total cholesterol (P<0.01), triglycerides (P<0.01), low-density lipoprotein (P<0.05), verylow- density lipoprotein (P<0.01) and atherogenic index (P<0.01). On the other hand, methanolic extracts of A. carambola stem and leaves showed the strongest antioxidant activity. Total phenolic and flavonoid contents of the extracts exhibited significant correlations with antioxidant but not with antihyperlipidemic activities. All plant parts showed no cytotoxic effect on the selected cancer or normal cell lines.
CONCLUSION: Antihyperlipidemic activity of different parts of A. carambola is greatly affected by extraction solvents used. Methanolic extract of A. carambola leaves exhibited higher antihyperlipidemic and antioxidant potentials compared to other parts of the plant.