Phenolic-rich extracts from selected tropical underutilized legumes inhibit α-amylase, α-glucosidase, and angiotensin I converting enzyme in vitro

BACKGROUND

In this study, interaction of free and bound phenolic extracts from selected tropical underutilized legumes (a popular folklore for the management of diabetes and hypertension) with key enzymes linked to type 2 diabetes (α-glucosidase and α-amylase) and hypertension (angiotensin I converting enzyme, ACE) was assessed.

METHODS

The free phenolic extracts of the soybean were obtained by extracting powdered legume seeds with 80% acetone, whereas the residue was subjected to alkaline and acid hydrolysis before extraction with ethyl acetate to obtain the bound extracts. Thereafter, enzyme (α-amylase, α-glucosidase, and ACE) inhibitory studies and antioxidant capacity of the extracts were investigated.

RESULTS

The free and bound phenolic extracts inhibited α-amylase, α-glucosidase, and ACE activities in a dose-dependent manner. However, the free phenolic extracts of all the legumes were stronger inhibitors of α-glucosidase than their corresponding bound phenolic extracts. In addition, the free phenolic extracts (except melon) exhibited stronger ACE inhibition than their corresponding bound phenolic extracts. All the phenolic extracts significantly (p<0.05) inhibited Fe2+-induced oxidative stress in the pancreas (in vitro) and exhibited strong antioxidant activities.

CONCLUSIONS

The inhibition of the α-amylase, α-glucosidase, ACE, and oxidative stress by the phenolic extracts could be a part of the mechanism through which these underutilized legumes manage/prevent type 2 diabetes and hypertension. However, as revealed by this study, bambara groundnut with the best enzyme inhibitory potentials coupled with strong antioxidant properties ranked highest, whereas melon seed ranked least.

Antioxidant and inhibitory effect of red ginger (Zingiber officinale var. Rubra) and white ginger (Zingiber officinale Roscoe) on Fe(2+) induced lipid peroxidation in rat brain in vitro

Neurodegerative diseases have been linked to oxidative stress arising from peroxidation of membrane biomolecules and high levels of Fe have been reported to play an important role in neurodegenerative diseases and other brain disorder. Malondialdehyde (MDA) is the end-product of lipid peroxidation and the production of this aldehyde is used as a biomarker to measure the level of oxidative stress in an organism. The present study compares the protective properties of two varieties of ginger [red ginger (Zingiber officinale var. Rubra) and white ginger (Zingiber officinale Roscoe)] on Fe(2+) induced lipid peroxidation in rat brain in vitro. Incubation of the brain tissue homogenate in the presence of Fe caused a significant increase in the malondialdehyde (MDA) contents of the brain. However, the aqueous extract from both varieties of ginger caused a significant decrease in the MDA contents of the brain in a dose-dependent manner. However, the aqueous extract of red ginger had a significantly higher inhibitory effect on both Fe(2+)-induced lipid peroxidation in the rat brain homogenates than that of white ginger. This higher inhibitory effect of red ginger could be attributed to its significantly higher phytochemical content, Fe(2+) chelating ability, OH scavenging ability and reducing power. However, part of the mechanisms through which the extractable phytochemicals in ginger (red and white) protect the brain may be through their antioxidant activity, Fe(2+) chelating and OH scavenging ability. Therefore, oxidative stress in the brain could be potentially managed/prevented by dietary intake of ginger varieties (red ginger and white ginger rhizomes).