Anti-hyperlipidemic activity of an extract from roots and rhizomes of Panicum repens L. on high cholesterol diet-induced hyperlipidemia in rats

1 Introduction

Hyperlipidemia is ranked as one of the greatest risk factors contributing to the prevalence and severity of coronary heart diseases [1]. Hyperlipidemia-associated lipid disorders are considered the cause of atherosclerotic cardiovascular disease [2].

The American Heart Association has identified elevated levels of cholesterol and triglycerides in the blood as the primary risk factor associated with atherosclerosis. Therefore, therapists consider the treatment of hyperlipidemia one of the major approaches towards decelerating the atherogenic process [3].

Allopathic hypolipidemic drugs are available at large in the market, but side effects and contraindications of these drugs have marred their popularity. Recently, herbal hypolipidemics have gained importance in overcoming these disadvantages [4].

Panicum repens L. (Poaceae) is a perennial grass that frequently forms dense colonies and has long, creeping rhizomes. It is primarily a weed of moist, coastal, sandy soils, although it also grows in heavy upland soils [5]. In Egypt, it is known as Nigeel farisi. It grows throughout the world in tropical and subtropical areas and is in many places an introduced species [6].

To the best of our knowledge, there is no report on biological activities of P. repens extracts, and, hence, in the current investigation the effect of an extract from this plant on high-cholesterol diet-induced hyperlipidemia in rats was studied.

2 Materials and methods

3 Results

3.2 Identification of phenolics and flavonoids

Phenolic acids and flavonoids were identified by comparing retention times and spectral characteristics with those of authentic standards.

Fraction B-7 contains gallic acid, chlorogenic acid, chicoric acid and primulic acid, whereas fraction E-12 contains chlorogenic acid, chicoric acid, primulic acid, rutin, apigenin-7-glucoside and quercetin (Table 2, Figure 1).

Table 2

Phenolic acids and flavonoids content of fractions B-7 and E-12.

Standard	Retention time (Rt), min
	B-7	E-12
Phenolics
Gallic acid	1.839	–
Chlorogenic acid	2.299	2.273
Chicoric acid	3.189	3.221
Primulic acid	4.006	4.062
Flavonoids
Rutin	–	5.343
Apigenin-7-glucoside	–	9.229
Quercetin	–	16.975
Hesperidin	–	–

Figure 1:

(A) HPLC analysis of Fraction B-7. (B) HPLC analysis of Fraction E-12.

Abscissa: time (min); ordinate: milli-absorbance units.

3.3 Effect of P. repens extract on plasma lipid profile

Table 3 summarizes the effects of the P. repens extract on the plasma lipid profile of the treated rats. Keeping the rats on a high-cholesterol diet significantly increased total cholesterol, triglycerides, LDL-cholesterol and total lipid level compared to the controls, p<0.05. The atherogenic index was significantly higher in cholesterol-treated rats.

Table 3

Effects of P. repens extract on serum lipid profile.

Group	Total lipids, mg/dL	TC, mg/dL	TG, mg/dL	HDL-C, mg/dL	LDL-C, mg/dL
Control	437±13.7	100.5±3.77	88.3±4.76	34±1.34	53.7±3
HFD	651±22.1a	131±9.6a	121±3a	26.3±2.1a	74.5±8a
HFD+E	213±15.7a, b	85.5±4.3a, b	71.2±4.6a, b	41.3±3.5b	30±3.4a, b
E	179±12.2a, b	80.5±0.6a, b	48.2±4.6a, b	45.5±4.7a, b, c	21±2.8a, b
HFD+R	219±15.2a, b	76±6.4a, b	46.6±4a, b	35.5±2.1b	31.5±2.3a, b
R	172±15.9a, b	81.5±4.11a, b	53±4.75a, b	35.4±1.7b	25±1.0a, b

Abbreviations as in legend to Figure 2. Results are expressed as mean±S.E. ^aSignificantly different from control group. ^bSignificantly different from High fat diet treated group. ^cGroup (HFD+E) and group (E) Significantly different from group (HFD+R) and (R).

Conversely, there was a significant decrease in the level of HDL-cholesterol in the cholesterol-treated rats, and the HDLC/LDL-C ratio was significantly decreased compared to the respective control values (p<0.05).

Treatment of all groups of rats with either the P. repens extract or the reference drug atorvastatin [13] resulted in a significant decrease of the levels of total cholesterol, triglycerides, LDL-cholesterol, and total lipids, as well as of the atherogenic index, as compared with the cholesterol-treated rats and the respective controls, p<0.05 (Figure 2).

Figure 2:

Atherogenic index in C, HFD, HFD+E, E, HFD+R and R treated groups.

C, control; HFD, high-fat diet; HFD+E, high-fat diet+extract; E, extract; HFD+R, high-fat diet+R (reference drug); R, reference drug. ^aSignificantly different from control. ^bSignificantly different from HFD.

The level of HDL-cholesterol and the HDLC/LDL-C ratio were significantly increased in all groups of rats treated with either the P. repens extract or atorvastatin when compared with the respective values in the cholesterol-treated group, p<0.05 (Figure 3).

Figure 3:

Ratio of HDL-C/LDL-C in C, HFD, HFD+E, E, HFD+R and R treated groups.

Abbreviations as in Figure 2. ^cSignificantly different from HFD+R and R.

4 Discussion

Development of atherosclerosis is a complicated process involving accumulation of lipid-containing particles in the walls of coronary arteries and other major arteries within the body. A high-fat diet causes cholesterol levels to increase in susceptible people, which leads to obesity [14].

Hyperlipidemia is a well-known risk factor for cardiovascular diseases, especially atherosclerotic coronary artery disease (CAD), which is one of the major causes of premature death globally [15]. Several studies revealed that an increase in HDL cholesterol and a decrease in TC, LDL cholesterol and TG are associated with a decreased risk of ischemic heart diseases [16]. Cholesterol feeding has often been used to elevate serum and tissue cholesterol levels to assess hypercholesterolemia-related metabolic disturbances in different animal models [17].

In the present work, as expected, a high-cholesterol diet significantly increased the levels of total lipids TC, TG and LDL-C in the serum and liver of rats, compared to animals on a normal diet. When the P. repens extract was co-administered with the cholesterol diet, the levels of these lipids were significantly reduced, whereas plasma HDL-C was increased and the atherogenic index was decreased, thereby confirming the anti-hyperlipidemic efficacy of the extract.

In a previous study, a 1% aqueous Panicum miliaceum L. grain extract [18] was found to effectively reduce hyperlipidemia in obese mice. The authors reported that this extract decreased monounsaturated fatty acid synthesis by inhibiting fatty acid uptake and chain elongation. Expression of hepatic lipogenesis-related genes (PPARα, L-FABP, FAS and SCD1) was decreased, whereas that of a lipolysis-related gene (CPT1) was increased.

The reduction of total cholesterol by the P. repens extract was associated with a decrease of its LDL fraction (LDL-C), which is the target of several hypolipidemic drugs. This result suggests that the cholesterol-lowering effect of the extract may result from the rapid catabolism of LDL-C through its hepatic receptors for final elimination in the form of bile acids as demonstrated by Khanna et al. [19].

The phytochemical analysis of the P. repens extract revealed the presence of alkaloids, flavonoids, saponins, tannins and carbohydrates. Some of these phytoconstituents are known to elicit a wide range of biological activities including hypoglycemic, hypolipidemic and hypoazotemic, among others [20]. Specifically, according to Oakenfull and Sidhu [21], saponins are known to lower serum cholesterol by a resin-like action. Some saponins with particularly defined structural characteristics form insoluble complexes with cholesterol (e.g. the well-known precipitation of cholesterol by digitonin). When this complexation process occurs in the gut, it inhibits the intestinal absorption of both endogenous and exogenous cholesterol. Conversely, saponins can interfere with the enterohepatic circulation of bile acids by forming mixed micelles. These can have molecular weights of several million, and the reabsorption of bile acids from the terminal ileum is effectively blocked. Also, saponins have been reported to increase fecal cholesterol excretion [22, 23].

5 Conclusion

The present study revealed the anti-hyperlipidemic action of the ethanolic extracts from P. repens rhizomes and roots. This finding provides some biochemical basis for the use of the P. repens extract against hyperlipidemia. Further studies are required to identify the active components and their mode of action.

Competing interests: The authors declare that there is no conflict of interest.