OLEANANE-TYPE TRITERPENOID SAPONIN OF MOMORDICA CYMBALARIA EXHIBITS NEUROPROTECTIVE ACTIVITY IN DIABETIC PERIPHERAL NEUROPATHY BY AFFECTING THE POLYOL PATHWAY

Momordica cymbalaria Fenzl (Cucurbitaceae) fruit powder and extracts are reported to have Type 1 antidiabetic activity in experimental diabetic models. The objective of this study was to investigate the neuroprotective action of an oleanane-type triterpenoid saponin isolated from the plant in diabetic peripheral neuropathy (DPN) by in vivo and in vitro methods. Male Wistar rats were rendered diabetic by administration of streptozotocin intraperitoneally. The rats were maintained for six weeks to induce neuropathy. Treatment groups received the saponin and epalrestat, an aldose reductase inhibitor. At the end of treatment, the animals were evaluated for various parameters of neuropathy like muscular grip strength and pain sensation tests using hot plate and tail-flick methods, and nerve conduction velocity (NCV) measurement. In vitro models of DPN were created by initiating sciatic nerve cultures of rats in 12-well plates. The nerve cultures were then rendered diabetic by exposing them to high glucose. After incubation of 7 days, the tissues were assayed for aldose reductase (AR) and sorbitol dehydrogenase (SDH) activities. Intraneuronal accumulation of sorbitol was also measured using HPLC method. The saponin exhibited significant reduction in the AR and SDH activities, reduction in the former being more prominent. Sorbitol accumulation in the nerves was also found to be less as compared to glucose control. Improvement of muscular grip strength, reaction time to pain sensation and nerve conduction velocity was demonstrated by the treated group. The results suggest that the saponin possesses significant neuroprotective activity and may prove to be good therapeutic agent for managing and treating diabetic neuropathy.