Rhinacanthins-rich extract: A potent superoxide scavenger and advanced glycation end-product formation inhibitor

Rhinacanthins-rich extract (RRE), containing 60% w/w rhinacanthin-C (RC), is a semi purified extract from Rhinacanthus nasutus leaf, a medicinal plant in Thai traditional medicine and an herbal drink in Taiwan and China. RRE was prepared and standardized by the previously described method [1] with some modifications using a microwave assisted extraction and an alternative green solvent. RC was isolated from the RRE using a silica gel column chromatography. In the current study, RRE and RC were determined for their superoxide reduction activity using a cyclic voltammetric method [2]. Furthermore, the in vitro inhibitory assay of RRE and RC was performed on human albumin glycation [3]. RRE and RC exhibited a potent and equal superoxide scavenging activity (via E_rC_i mechanism), with the IC₅₀ values of 8.0 and 9.6 µg/mL as well as antiglycation activity, with the IC₅₀ values of 39.7 and 37.3 µg/mL, respectively. The structure activity relationship of RC was explained by molecular docking studies that identified the interaction of RC with albumin to mask it from non-enzymatic glycation (Fig. 1). The potent superoxide scavenging and significant antiglycation activities of RRE streamlined its potential role in diabetic complications.

Fig. 1: The visual depicting the binding mode of rhinacanthin-C in the Sudlow's sites of human serum albumin.

TEH-AC PhD Award 2014 by Prince of Songkla University Hat Yai Thailand, and GA Travel Grant, 2017.

[1] Panichayupakaranant P, et al. J Chromatogr Sci 2009; 47:705 – 708.

[2] Muhammad H, et al. J Electroanal Chem 2016; 775:157 – 162.

[3] Khan MK, et al. Med Chem 2011; 7:572 – 580.