Efficient Separation of Phytochemicals from Muehlenbeckia volcanica (Benth.) Endl. by Polarity-Stepwise Elution Counter-Current Chromatography and Their Antioxidant, Antiglycation, and Aldose Reductase Inhibition Potentials.

Guang-Lei Zuo,Hyun Yong Kim,Yanymee N Guillen Quispe,Zhi-Qiang Wang,Kyong-Oh Shin,Soon Sung Lim,Seung Hwan Hwang

doi:10.3390/molecules26010224

Abstract

Muehlenbeckia volcanica (Benth.) Endl. (M. volcanica), native to South America, is a traditional Peruvian medicinal plant that has multi-therapeutic properties; however, no phytochemicals have been identified from it yet. In this study, a five-step polarity-stepwise elution counter-current chromatography (CCC) was developed using methanol/water (1:5, v/v) as the stationary phase and different ratios of n-hexane, ethyl acetate, and n-butanol as mobile phases to separate the compounds from the 70% methanol extract of M. volcanica, by which six compounds with a wide range of polarities were separated in a single run of CCC and were identified as gallic acid, protocatechuic acid, 4,4′-dihydroxy-3,3′-imino-di-benzoic acid, rutin, quercitrin, and quercetin. Then, two compounds from the fractions of stepwise elution CCC were separated using conventional high-speed CCC, pH-zone-refining CCC, and preparative high-performance liquid chromatography, and identified as shikimic acid and miquelianin. These compounds are reported from M. volcanica for the first time. Notably, except for shikimic acid, all other compounds showed anti-diabetic potentials via antioxidant, antiglycation, and aldose reductase inhibition. The results suggest that the polarity-stepwise elution CCC can be used to efficiently separate or fractionate compounds with a wide range of polarities from natural products. Moreover, M. volcanica and its bioactive compounds are potent anti-diabetic agents.

Highlights

Targeting antioxidants, advanced glycation end products (AGEs), and aldose reductase (AR) as potential therapeutic approaches for the prevention and amelioration of diabetic complications has attracted growing interest [1,2,3]
The results were expressed as Trolox equivalent antioxidant capacity (TEAC, μg Trolox/μg extract), which were calculated with the equations obtained from the calibration curves of Trolox standards versus their DPPH and ABTS radical inhibition (%) and the net area under the curve (AUC) value (ORAC assay)
A larger TEAC value indicates that the sample tested has higher antioxidant activity

Summary

Introduction

Targeting antioxidants, advanced glycation end products (AGEs), and aldose reductase (AR) as potential therapeutic approaches for the prevention and amelioration of diabetic complications has attracted growing interest [1,2,3]. In hyperglycemia conditions, an important diabetic characteristic [4], the polyol pathway flux is significant in insulin-independent tissues, such as lens, glomerulus, and neural tissue, and it may cause a decrease in cytosolic NADPH/NADP+ and an increase in cytosolic NADH/NAD+ leading to ROS production and oxidative stress in those tissues. Since ROS, AGEs, and the sorbitol-induced osmotic stress play an important role in the development of diabetic complications, such as diabetic neuropathy, retinopathy, and nephropathy [8], antioxidants, antiglycation agents, and inhibitors of AR, a key enzyme in the polyol pathway, have therapeutic potential for diabetic complications [1,2,3]

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