Novel cholinesterase inhibitory effect of α-spinasterol isolated from the leaves of Acacia auriculiformis A. CUNN Ex. Benth (Fabaceae)

Purpose: To investigate the in vitro anticholinesterase, α-glucosidase and antioxidant activities of α-spinasterol isolated from Acacia auriculiformis leaves.Methods: The powdered leaves of Acacia auriculiformis were extracted with 70 % ethanol and the dried hydroalcoholic extract was suspended in water and partitioned with ethyl acetate and n-butanol to give their soluble fractions. The in vitro inhibitory activities of α-spinasterol were determined against cholinesterase and, α-glucosidase enzymes, and free radical scavenging potentials using (1,1-diphenyl-2-picrylhydarzyl (DPPH) and 2,2-azino-bis (3-Ethylbenzothiazoline-6-sulphonic acid (ABTS) antioxidantassays.Results: The compound, α-spinasterol, exhibited moderate anticholinesterase activity (IC50 value of 44.19±2.59 μg/mL which was significantly different at (p < 0.05) when compared to the standard galanthamine (IC50 value of 1.73 ± 1.10 μg/mL). It also displayed a good α-glucosidase inhibitory activity with IC``` value of 8.65 ± 1.71μg/mL which was not significantly different when compared to the standard, acarbose with IC50 value of 2.79±0.81 μg/mL. This compound, however, exhibited weak free radical scavenging activities at 26.93 ± 0.00 and 35.16 ±.0.26 % inhibition of DPPH+ and ABTS+ radicals as compared to ascorbic acid and Trolox (73.88 ± 0.04 and 99.82 ± 0.00%) respectively.Conclusion: The results show that α-spinasterol isolated from Acacia auriculiformis exerts potent inhibitory effect against cholinesterase enzyme which might serve as a lead in the search for drugs against Alzheimer disease and diabetes mellitus. Keywords: Acacia auriculiformis, α-Spinasterol, Galanthamine, Acarbose, Trolox, Ascorbic acid