Inhibitory activities of ten accessions of underutilised West Africa legume Macrotyloma geocarpum (Harms) Maréchal & Baudet, growing in Nigeria against metabolic enzymes α-amylase and α-glucosidase

Underutilised legumes are important crop species whose cultivation and consumption are declining despite their medicinal and nutritional benefits. One of the most pressing global health concerns of the twenty-first century is diabetes, characterised by elevated blood sugar levels (hyperglycaemia). Food plays a huge role in the incidence and management of metabolic diseases such as diabetes. Hence, pharmacological research along the food-medicine continuum is being ignited by recent evidence linking diet to health and illness incidence. Herein, we determined in vitro the inhibitory effects of the gene bank-stored seed and freshly cultivated seed and leaf extracts of ten accessions of an underutilised legume (Macrotyloma geocarpum) on the enzymes involved in carbohydrate breakdown to glucose (α-amylase and α-glucosidase) as a strategy to reduce hyperglycaemia. The extracts of seed accessions obtained from the gene bank showed weakly α-amylase inhibition (IC50 range = 300–1000 µg/mL) while, extracts of the cultivated seed accessions generally showed enhanced inhibitory effects (IC50 range = 63–355 µg/mL), when compared to standard Acarbose® (IC50 = 64.23 ± 0.02 µg/mL). Freshly harvested seed accessions (72–616 µg/mL) were also observed to have enhanced inhibitory effects on α-glucosidase enzyme than the seeds from the gene bank (39–185 µg/mL) when compared to Acarbose® (73.23 ± 0.02 µg/mL). However, the leaf extracts of the cultivated accessions displayed significantly higher α–amylase inhibition (IC50 range = 54–61 µg/mL) than the cultivated seeds while a reversed case was observed in the α–glucosidase inhibition. Overall, this study suggests the medicinal importance of the underutilised M. geocarpum legume in the management of diabetes while considering the varying bioactive effects of the accessions as well as cultivation and storage.