New free radical scavenging neolignans from fruits of Piper attenuatum

Objective: The aim was to study and identify free radicals scavenging and antihyperglycemic principles in fruit of Piper attenuatum. Materials and Methods: Bioassay guided identification of extracts possessing potent free radical scavenging activity, and isolation of compounds was done. Chloroform extract of P. attenuatum possessing potent radical scavenging activity was also evaluated for antihyperglycemic activity following oral glucose tolerance test in rats. Results: Nine neolignans namely, denudatin B (1), iso-4', 5'- dimethoxy-3, 4-methylenedioxy-2'-oxo-Δ ^3',5',8' -8.1'- lignan (2), lancifolin D (3), denudatin A (4), wallichinin (5), piperenone (6), lancifolin C (7), 2-oxo-piperol B (8), piperkadsin A (9) and a crotepoxide (10) was identified in Chloroform extract of P. attenuatum. Neolignans (1-9) displayed potent 2, 2'- azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) radical and piperkadsin A (9) also displayed 1, 1-diphenyl-2-picrylhydrazyl radical scavenging activity. Analysis of structure-activity relationship revealed that presence of furan ring and methoxy groups is an important criterion to influence 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging potentials. Chloroform extract of P. attenuatum fruit could not display antihyperglycemic activity following oral glucose tolerance test in rats. Conclusion: Neolignans present in P. attenuatum fruits are potent free radical scavengers and this is the first report identifying these compounds and activities in this fruit.