Tirawanchai N , Somkasetrin A , Kengkoom K, Ampawong S Study on a cholesterol-lowering effect of Cymbopogon citratus in a human hepatocellular carcinoma cell line Tirawanchai N , Somkasetrin A , Kengkoom K, Ampawong S

Hypercholesterolemia INTRODUCTION Hypercholesterolemia Is commonly recognised in the population worldwide including Thai population. It increases with age (1). It is widely accepted as a major risk factor for cerebrovascular diseases (CVD). Figure 1 Hypercholesterolemia can lead to development of atherosclerosis in a coronary artery and CVD (2).

3-Hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase (HMGCR), a membrane-bound enzyme is the rate-limiting enzyme for cholesterol biosynthesis in the human body(3). Figure 2 Cholesterol biosynthesis (4).  The HMGCR enzyme is a therapeutic target for Statin drugs to lower blood cholesterol levels which leads to reduce the risks of CVD (5).

Figure 3 Lemongrass plant (7). Cymbopogon citratus Commonly known as lemongrass, is an aromatic perennial grass belonging to the family grimneae(6). It is an important tropical plant from SoutheastAsia including Thailand. Figure 3 Lemongrass plant (7). 

C. citratus is widely used in Thai folk medicine and ayurveda remedies. It has been reported that C. citratus extract had hypolipidemic and hypoglycemic potentials on alloxan-induced diabetic rats (8). Therefore, it is proposed that ethanol-extract of C. citratus might be an alternative choice for lowering blood cholesterol levels by inhibition of the HMGCR enzyme in cholesterol biosynthesis.

Ethanol-extract of C. citratus Objectives This project aims to study the effect of C. citratus ethanol-extract on the expression of the HMGCR gene involving in cholesterol biosynthesis Materials and Methods Ethanol-extract of C. citratus Fresh leaves and stems of C. citratus was air-dried before subjection to ethanol-extract(8).

Effect of C. citratus on HMGCR gene expression Cell culture (HepG2 cells) Negative control (0.5%DMSO) C. citratus ethanol-extract Positive control (Simvastatin) Cytotoxicity Gene expression RNA extraction MTT assay cDNA synthesis qRT-PCR

Concentrations of C. citratus (mg/ml) Results Cytotoxic effect of the ethanol-extract of C. citratus on HepG2 cells viability C. citratus treatment was less toxic to HepG2 cells than simvastatin treatment (IC50 = 1.31 versus 0.07 mg/mL, respectively). R2 = 0.8481 A B % Cell viability Concentrations of C. citratus (mg/ml) Figure 4 Effect of C. citratus (A) and simvastatin (B) on HepG2 cell viability. Data were shown as mean ± S.D, (n = 3).

Effect of the ethanol-extract of C. citratus on HMGCR gene expression C. citratus treatment significantly down-regulated the HMGCR gene expression in HepG2 cells at all concentrations when compared with the negative control. On the contrary, simvastatin showed upregulation of the HMGCR gene expression compared to the negative control. Figure 5 Quantitative RT-PCR analysis of the HMGCR gene expression in C. citratus or simvastatin-treated HepG2 cells for 24 h. Data were shown as mean ± S.D, (n = 3). Fold expression mg/ml

Discussion and Conclusion It was demonstrated that ethanol-extract of C. citratus was more effective than simvastatin in down-regulation of the HMGCR gene expression. However, simvastatin has a primary action to inhibit the enzyme activity(5). Therefore, further studies on the effect of C. citratus and its active compounds on protein levels and other genes involving in the cholesterol homeostasis may help provide a better understanding of cholesterol-lowering potential of C. citratus. Acknowledgement This project was financially supported by Mahidol University.

References 1) Aekplakorn W, Taneepanichskul S, Kessomboon P et al., J Lipids 2014; http://dx.doi.org/10.1155/2014/249584. 2) https://en.wikipedia.org/wiki/Coronary_artery_disease 3) Goldstein JL, Brown MS. Regulation of the mevalonate pathway. Nature 1990; 343(6257): 425-30. 4) https://med.libretexts.org/ 5) Stroes E. Statins and LDL-cholesterol lowering: an overview. Curr Med Res Opinion 2005; 21 Suppl 6: S9-16. 6) Ebomoyi O. Traditional Medicine in Mental health care. J Am Sci 2008; 4: 21-25. 7) http://extension.illinois.edu/herbs/lemon-grass.cfm 8) Ewenighi CO, Uchechukwu D, Adejumo BI et al. Estimation of lipid profile and glucose level in alloxan-induced diabetic rats treated with Cymbopogon citratus (lemongrass). J Exp Integr Med 2013; 3(3): 249-53.