Antihyperglycaemic and antioxidant activities of Sansevierialiberica as justification for its antidiabetic claims

Diabetes has become a global emergency because of its high prevalence, morbidity and mortality while the available hypoglycaemic drugs possess various adverse effects and are expensive. This has necessitated a continuous search for cheaper antidiabetic agents of plant origin with fewer or no side effects. The study evaluated the antihyperglycaemic activities of the methanol extract of Sansevieria liberica Gerome and Labroy (Agavaceae) rhizome. Both the partitioned and column fractions were tested on glucose-induced hyperglycaemic rats while their in vitro antioxidant effects studied using 1,1-diphenyl-2-dipicrylhydrazyl radical scavenging (DPPH), ferric reducing antioxidant power (FRAP), total antioxidant capacity (TAC), hydroxyl radical scavenging activity (HRSA) as well as the  total phenolic content (TPC) and total flavonoid content (TFC) assays. Glibenclamide (5 mg/kg) and appropriate anti-oxidant standard drugs were used as positive controls. The estimated median lethal dose (LD50) of the methanol extract was 3,808.0 mg/kg; at 100, 200 and 400 mg/kg, it gave comparable (p>0.05) antihyperglycaemic activity to glibenclamide at 5 mg/kg. Its ethyl acetate fraction at 200 and 400 mg/kg gave the highest antihyperglycaemic activities of 49.5 and 53.9%, respectively, the highest antioxidant activities in all the models used. The highest antihyperglycaemic and antioxidant values were observed in the column fractions, C3, C4 and C7 of the ethylacetate partitioned fraction. The comparable antihyperglycaemic activity to glibenclamide of the methanol extract of S. libericarhizome in this study has justified its ethnomedical claims as antidiabetic agent. The consistently high antihyperglycaemic and antioxidant activities of the extract and its partitioned and column fractions would suggest a direct relationship between the two biological activities investigated. Key words: Diabetes mellitus, Sansevierialiberica, anti-hyperglycaemic activity, antioxidant activity.