a-Amylase inhibitory effect of 3b-olean-12-en-3-yl (9Z)-hexadec-9-enoate isolated from Spondias mombin leaf Adediwura Fred-Jaiyesimi a, * , Abo Kio b , Wilkins Richard a a School of Biology, University of Newcastle Upon Tyne, Newcastle Upon Tyne, NE1 7RU, United Kingdom b Faculty of Pharmacy, University of Ibadan, Nigeria article info Article history: Received 24 January 2008 Received in revised form 6 March 2008 Accepted 17 February 2009 Keywords: Spondias mombin a-Amylase inhibitor Diabetes abstract Spondias mombin is a traditional herb used in the treatment of diabetes mellitus by traditional healers in southwest Nigeria. In this study, we investigated the antidiabetic activity using a-amylase inhibitory assay and isolated an active compound. The bioactivity assay-guided study demonstrated the presence of an a-amylase inhibitory fraction from S. mombin leaf. An active compound, 3b-olean-12-en-3-yl (9Z)-hexadec-9-enoate was also studied. This is reported, from this plant, for the first time. The methanol extract, diethyl ether fraction and the isolated compound exhibited significant enzyme inhibitory activity against Aspergillus oryzae a-amylase. Our study revealed, for the first time, the isolation and a-amylase inhibitory activity of 3b-olean-12-en-3-yl (9Z)-hexadec-9-enoate from S. mombin leaf. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Non-insulin-dependent diabetes mellitus is a heterogeneous disease with both genetic and environmental causative factors. It is characterised by hyperglycaemia caused by decrease in the secretion of insulin from the pancreatic Langerhans b-cells. A new alternative therapeutic approach of treating non-insulin dia- betes mellitus involves inhibiting a-amylase and a-glucosidase. These are the key enzymes involved in starch breakdown and intestinal absorption. The inhibition of these enzymes significantly decreases the digestion and uptake of carbohydrate, thereby decreasing the postprandial blood glucose level in the non-insu- lin-dependent diabetes mellitus patients (Puls, Keup, Krause, Tho- mas, & Hoffmeister, 1977). Acarbose and voglibose are currently used as a-amylase and a- glucosidase inhibitors and have exhibited side effects such as abdominal distension, bloating, flatulence and diarrhoea (Chakrab- arti & Rajagopalan, 2002; Kimmel & Inzucchi, 2005). These side ef- fects are possibly caused by excessive inhibition of the pancreatic a-amylase, leading to bacterial fermentation of undigested carbo- hydrate in the colon (Bischoff, 1994). Several studies have reported the isolation of a-amylase and a- glucosidase inhibitors from dietary plants. These isolated inhibi- tors have been reported to be effective in decreasing postprandial hyperglycaemia with minimal side effects (Kwon, Vattem, & Shetty, 2006). Hence a search has ensued for a-amylase inhibitors from plants used by traditional healers in southwest Nigeria for the treatment of diabetes mellitus. Spondias mombin Linn (Anacardiaceae) is a deciduous tree found in forest and Savannah regions (Hutchinson, 1959). It is used traditionally as food and for its medicinal values. The young leaves are cooked as greens and the green fruits pickled in vinegar and eaten like olives with salt and chilli. The aromatic fruit of S. mombin, rich in vitamins B1 and C, are eaten as a means of alleviating thirst, to flavour drinks and ice cream and mainly to produce wine, sold as ‘‘Vinho de Taperida” (Moran, 1987). In traditional folklore medicine, S. mombin is used to treat diabetes, intestinal disorders, typhoid fever and as an abortifacient. Various parts of S. mombin have been reported to exhibit var- ious biological effects, such as antidiarrhoeal activity (Iwu, 1993), antimicrobial and astringent effect (Abo, Ogunleye, & Ash- idi, 1999; Kokwaro, 1976; Oliver-Bever, 1960), antipsychotic effect (Ayoka, Akomolafe, Iwalewa, Akanmu, & Upkonmwan, 2006), antiinflammatory activity (Villegas et al., 1997), as an abortifacient (Offiah & Anyanwu, 1989), for antiviral activity (Corthout, Pieters, Claeys, Vanden Berghe, & Vlietinck, 1991, 1992) and beta lactamase inhibitory activity (Coates et al., 1994). There is, however, no report of the antidiabetic activity of S. mombin. A bioactivity-guided study of the leaf of S. mombin was carried out to investigate the a-amylase inhibitory effect of S. mombin fractions and to isolate the compound responsible for the inhibi- tory activity. 0308-8146/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2009.02.047 * Corresponding author. Tel.: +44 7903120990. E-mail address: adediwurajaiyesimi@gmail.com (A. Fred-Jaiyesimi). Food Chemistry 116 (2009) 285–288 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem