Hypoglycemic effect of the hydroalcoholic extract of leaves of Averrhoa carambola L. (Oxalidaceae)

Abstract

RESUMO: "Efeito hipoglicemiante do extrato hidroalcoólico de folhas de Averrhoa carambola L. (Oxalidaceae)". O efeito do tratamento via oral (20 mg/kg x day) com extrato hidroalcoólico de folhas de Averrhoa carambola L. (EHFC) sobre a glicemia de jejum (15 h) foi examinada ao compararmos ratos que receberam veículo (Grupo controle) ou EHFC (Grupo EHFC) durante 15 dias. O grupo EHFC apresentou menor glicemia de jejum (p 0,05). Em contraste, o grupo EHFC apresentou maior (p 0,05) produção hepática glicose a partir de L-alanina (5 mM). Este efeito foi mediado, pelo menos parcialmente, pela ativação do catabolismo da L-alanina, inferido pela maior produção hepática de uréia (p 0,05) e L-lactato (p 0,05). Diferente da L-alanina, a produção hepática de glicose a partir de L-glutamina (5 mM), L-lactato (2 mM) e glicerol (2 mM) no grupo EHFC foi similar ao grupo controle. Adicionalmente, o efeito do tratamento com EHFC sobre a captação de glicose no músculo soleus, inferida pela incorporação de [14 C]-glicose em glicogênio (síntese de glicogênio) e produção de [14 C]-lactato foi investigada, verifi cando-se resultados semelhantes nos dois grupos. Assim, concluiu-se que a redução da glicemia de jejum promovida pelo tratamento com EHFC não foi mediada por inibição da gliconeogenese hepática e/ou aumento da captação muscular de glicose.Unitermos: Averrhoa carambola, Oxalidaceae, carambola, gliconeogenese, plantas antidiabeticas, efeito hipoglicemiante. ABSTRACT:The effect of the oral treatment (20 mg/kg x day) with the hydroalcoholic extract of leaves of Averrhoa carambola L. (HELAC) on fasting glycemia (15 h) was examined. For this purpose, rats that received vehicle (Control group) or HELAC (HELAC group) during 15 days were compared. HELAC group showed lower fasting glycemia (p 0.05). In contrast, livers from HELAC group showed higher (p 0.05) glucose production from L-alanine (5 mM). This effect was mediated, at least part of it, by an activation of the catabolism of L-alanine inferred by the increased hepatic urea (p 0.05) and L-lactate (p 0.05) production. Differently of L-alanine, the glucose production from L-glutamine (5 mM), L-lactate (2 mM) and glycerol (2 mM) was similar (Control group vs. HELAC group). In addition, the HELAC treatment did not change the glucose uptake in soleus muscles, inferred by the incorporation of [ 14 C]-glucose to glycogen (glycogen synthesis) and [14 C]-lactate production. Thus, we can conclude that the reduction of fasting glycemia promoted by the treatment with HELAC was not mediated by an inhibition of hepatic gluconeogenesis and/or an increased glucose uptake by muscles.

Chemical constituents and evaluation of the toxic and antioxidant activities of Averrhoa carambola leaves

“…The species A. carambola presents hypoglycemic (Chau et al, 2004a;Ferreira et al, 2008), hypocholesterolemic (Chau et al, 2004b), antimicrobial (Hsu et al, 2007), antioxidant (Shui & Leong, 2006), and anti-infl ammatory (Cabrini et al, 2011) effects. An alcoholic extract of the stems of A. carambola has been shown to exhibit selective activity against brain tumor cells while that of the leaves was effective against liver carcinoma cells (Tadros & Sleem, 2004).…”

Antioxidant and antimicrobial activities of Penicillium sp. lectins

“…The ability of Penicillium sp. lectin solution to scavenge hydrogen peroxide radicals was determined as described [44] where Abs A is the absorbance of the control reaction and Abs B is the absorbance of the lectin solution. The half maximal inhibitory concentration (IC 50 ) was determined as described above.…”

A Comprehensive Review of An Important Medicinal Plant – Averrhoa carambola L.

“…[24] Treatment with hydroalcholic extracts of the leaves resulted in reduction in fasting glycemia, which was not mediated by an inhibition of hepatic gluconeogenesis and / or an increased glucose uptake by muscles. [25] Hydro alcoholic extracts of the leaves also showed anti-ulcer activity, with a different mechanism of action for the anti-ulcerogenic activity. As hydro alcoholic extract contains triterpenes, flavonoids, and mucilage, the partial anti-ulcer activity could be due to their effects.…”

“…[28] It is also possible that these high flavonoid contents may act in a synergistic manner with other A. carambola components to achieve these bioactivities. Ferreira et al [25] reported that the reduction of fasting glycemia promoted by the treatment with hydroalcoholic extracts of the leaves was not mediated by an inhibition of hepatic gluconeogenesis and/or an increased glucose uptake by muscles.…”