Sphingomyelinase inhibitory and free radical scavenging

Abstract

Ceramides from sphingolipid breakdown, and other sphingolipid metabolites, mediate cellular signalling ininfectious and other diseases. Therefore, inhibitors of sphingomyelinases (SMases), hold promise as prospective therapeuticagents. Considering the potential therapeutic utility, this in vitro study explored the sphingomyelinase inhibitory, and freeradical scavenging potential of five Nigerian medicinal plant leaf extracts, purported to have efficacy against diseases, includingHIV/AIDS. The extracts’ sphingomyelinase inhibitory potencies were assessed colorimetrically and their free radical scavengingcapabilities were assayed by the ability to quench 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical and superoxide anion (O2.‐)radical. Considering their IC50 (μg/ml) values, the extracts inhibited the biochemical activity of sphingomyelinase in a dosedependent manner, relative to imipramine the standard inhibitor (IC50 38.5 ± 2.4 μg/ml). With Aloe vera as least inhibitory,inhibition increased as follows: Aloe vera (Asphodelaceae) (1132 ± 10.8) < Senna siamea (Fabaceae) (992.2 ± 11.2) < Azadirachtaindica (Meliaceae) (984 ± 7.4) < Landolphia owariensis (Apocynaceae) (146.3 ± 9.4) < Stachytarpheta angustifolia (Verbenacae)(100.3 ± 8.7). DPPH radical scavenging relative to ascorbic acid standard increased as: A. indica < A. vera < S. siamea < S.angustifolia < L. owariensis; and superoxide anion quenching, relative to standard rutin increased as: A. vera < S. angustifolia < L.owariensis < S. siamea < A. indica. These results showed that the most potent SMase inhibitor was S. angustifolia; whereas, forDPPH radical scavenging and superoxide inhibition, the most potent of the five extracts were L. owariensis and A. indicarespectively. These extracts deserve further investigation into their biological effects.