Investigation of potential anti-diabetic effect of Mucuna pruriens (L) DC (Fabaceae) aqueous leaf extract.

Mucuna pruriens (L.) DC is an herbal plant popularly used in parts of Africa for the treatment of anaemia and in some parts of Asia for treatment of diabetes [1,2]. The antidiabetic effect of alcoholic leaf extract of Mucuna pruriens (MP) has been studied previously in diabetic rats [3]; however, the potential antidiabetic effect of an aqueous extract has not been evaluated.

MP leaves were identified and stored at the herbarium in the International Centre for Ethnomedicine and Drug development, Nigeria, West Africa. The specimen identification number is: InterCEDD-16018. We investigated the effect of an aqueous extract of Mucuna pruriens leaves (MPLE) on glucose uptake in rat NRK-52E renal cell line. Diethyl ether fractions from acid hydrolysis of MPLE (DE and NDE) and MPLE were also evaluated for insulin mimetic activity in differentiated 3T3-L1 adipocytes. Phenolics in MPLE were detected using HPLC-UV/VIS. The peaks where identified by comparison with reference peaks obtained for known flavonoids and phenolic acids.

Identified phenolics included Epicatechin, Rutin, Gallic acid, Caffeic acid, Coumaric acid, and Ellagic acid. 1 mg/ml MPLE inhibited glucose uptake in NRK-52E cell lines by 35.5%. This effect was comparable to 1mM Phloridzin (a standard sodium glucose transporter inhibitor). The extracts at 50 and 100 µg/ml stimulated glucose uptake by 65.97% and 78.25% of 15 ng/ml Insulin respectively.

Fig. 1: Comparison of the effect of 50 µg/ml MPLE and 50 µg/ml MPLE acid hydrolysed fractions on glucose uptake in 3T3-L1 adipocytes. * Shows significant difference in glucose uptake stimulatory effect compared to the negative control at p < 0.05 (one way ANOVA followed by a Bonferroni's post test). Data represents mean value ± S.D 8 replicates (n = 8).

Fig. 2: Comparison of the effect of 100 µg/ml MPLE and 100 µg/ml MPLE acid hydrolysed fractions on glucose uptake in 3T3-L1 adipocytes. * Shows significant difference in glucose uptake stimulatory effect compared to the negative control at p < 0.05 # shows significant difference in glucose uptake stimulatory effect between DE 100 µg/ml and CE l00 µg/ml at p < 0.05 (one way ANOVA followed by a Bonferroni's post test). Data represents mean value ± S.D 8 replicates (n = 8).

Fig. 3: Effect of MPLE on glucose uptake in NRK-52E cell lines using. *Shows significant difference compared to 2-NBDG only. # shows significance compared to the blank measured at p < 0.05 (one way ANOVA followed by Dunnett's multiple comparison test). Data represents mean ± SD of 9 replicates (n = 9).

Fig. 4: Detection and quantification of known Phenolics in AMPLE using HPLC/UV-vis recorded at 280nm (A), 320nm (B), 360nm (C). Peak Identification: l – Gallic acid, 2 – Vanillic acid, 3 – Catechin, 4 – Protocatechuic acid, 5 – Caffeic acid, 6 – Epicatechin, 7 – Ellagic acid, 8 – Coumaric acid, 9 – Ferulic acid, 10 – Rutin, 11 – Myricetin

MPLE could exert anti-diabetic effects via multiple mechanisms of action.

[1] Lampariello LR, Cortelazzo A, Guerranti R, Sticozzi C, Valachi G. J. Tradit Complement Med 2012; 2: 331 – 339

[2] Akindele AJ, Busayo FL. Nig Q Hosp Med 2011; 21: 93 – 98

[3] Murugan M, Reddy CUM. J Pharm Sci Technol 2009; 1: 69 – 73