Antioxidant Activity in Rheum emodi Wall (Himalayan Rhubarb)

Abstract

Using natural products as antioxidant agents has been beneficial to replace synthetic products. Efforts have been made to profile the antioxidant capacities of natural resources, such as medicinal plants. The polyphenol content of Himalayan rhubarb, Rheum emodi wall, was measured and the antioxidant activity was determined using DPPH and ABTS+ assay, and the oxidative stress was assessed using SOD enzymatic assay. Five different solvent fractions, n-hexane, n-butanol, ethyl acetate, dichloromethane, and water, were used for screening the antioxidant capacity in effort to determine the optimum extraction solvent. The total phenolic contents for R. emodi fractions ranged from 27.76 to 209.21 mg of gallic acid equivalents (GAE)/g of dry weight. DPPH and ABTS+ assay results are presented into IC50 values, ranged from 21.52 to 2448.79 μg/mL and 90.25 to 1718.05 μg/mL, respectively. The ethyl acetate fraction had the highest antioxidant activity among other fractions. Also, n-butanol and water fractions showed significantly lower IC50 values than the positive control in DPPH radical scavenging activity. The IC50 values of SOD assay of fractions ranged from 2.31 to 64.78 μg/mL. A similar result was observed with ethyl acetate fraction showing the highest SOD radical scavenging activity. The study suggests that the ethyl acetate fraction of R. emodi possess the strongest antioxidant activity, thus the most efficient in extracting antioxidant contents. Moreover, a highly significant correlation was shown between total polyphenol content and antioxidant activity screening assays. The compounds related to the antioxidant activity of R. emodi were identified to myricitrin, myricetin 3-galloyl rhamnoside, and myricetin, which have not been reported in studies about R. emodi before.

Phytochemical content and antioxidant activities of Rhubarb (<i>Rheum emodi</i>)

“…The quantity of TPC was calculated by a regression equation of a standard curve, y = 0.0009x + 0.1441, R 2 = 0.964, and ranged from 854.791 to 897.847 mg GPE per g of dry extract weight. The phenolic content in R. emodi water extract was higher than the n-butanol, ethyl acetate, n-hexane, dichloromethane, and water extracts reported by the study done by Park lee (Park & Lee, 2021). They reported that the lowest TPC is in the n-hexane extract of R. emodi was 27.76 mg GAE/g, while the highest amount is seen in ethyl acetate was 209.21 mg GAE/g.…”

Antioxidant Activities of Bioactive Compounds Isolated from Rheum emodi Wall (Himalayan Rhubarb) Based on LC-DAD-ESI/MS and Preparative LC/MS System

“…According to Park et al (2021) , the polyphenol contents and antioxidant activities of the ethyl acetate fraction were the greatest. It was chosen as an extraction solvent for further investigation into the identification of antioxidant compounds using HPLC with gradient elution.…”

“…Fig. 1 shows that the samples were prepared following the method ( Park et al, 2021 ). The plant materials were air-dried, and 800 g of the sample were powdered and extracted with 70% ethanol under reflux (3×2.5 L, 2 h each time), then filtered through Whatman No.…”

“…The ABTS radical scavenging activity was used to determine the total antioxidant activity of the samples ( Re et al, 1999 ) as described by Park et al (2021) . The ABTS + was produced by reacting 7 mM ABTS in H 2 O with 2.45 mM potassium persulfate (K 2 S 2 O 8 ) and stored in a dark at room temperature for 12∼16 h. It was then diluted with 99.5% ethanol to obtain an absorbance of 0.70±0.02 at 734 nm.…”

“…The compounds present in R. emodi fractions were isolated following the method ( Park et al, 2021 ) using Micromass ZQ MS (Waters Corp., Milford, MA, USA) and an Alliance e2695 high-performance liquid chromatography (HPLC) system (Waters Corp.) equipped with a 2998 photodiode array detector (PDA). In addition, the reversed-phase column YMC PACK ODS-AM (4.6×250 nm I.D., 5 m, YMC Co., Ltd., Kyoto, Japan) was used.…”