Antioxidant and hepatoprotective effects of Schisandra chinensis pollen extract on CCl₄-induced acute liver damage in mice

Abstract

The aim of the present study was to investigate the antioxidant and hepatotective effects of Schisandra chinensis pollen extract (SCPE) on CCl₄-induced acute liver damage in mice. Total phenolic content, total flavonoid content, individual phenolic compounds and antioxidant activities (1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, chelating activity, and reducing power assay) were determined. In vivo study, SCPE (10, 20 and 40 g/kg) administered daily orally for 42 days prior to CCl₄-intoxicated. Our results showed that SCPE had high total phenolic content (53.74 ± 1.21 mg GAE/g), total flavonoid content (38.29 ± 0.91 mg Rutin/g), quercetin and hesperetin may be the major contributor to strong antioxidant activities. Moreover, SCPE significantly prevented the increase in serum ALT and AST level in acute liver damage induced by CCl₄, decreased the extent of malondialdehyde (MDA) formation in liver and elevated the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in liver. The results indicated that SCPE has strong antioxidant activities and significant protective effect against acute hepatotoxicity induced by CCl₄, and have been supported by the evaluation of liver histopathology in mice. The hepatoprotective effect may be related to its free radical scavenging effect, increasing antioxidant activity and inhibiting lipid peroxidation.

Introduction

Carbon tetrachloride (CCl₄) is one of the oldest and most widely used toxins for experimental induction of liver injury in laboratory animals (Brautbar and Williams, 2002). It is generally accepted that the hepatotoxicity of CCl₄ is the result of reductive dehalogenation, which is catalyzed by hepatic cytochrome P-450, and which forms unstable trichloromethyl (CCl₃) and trichloromethyl peroxyl (CCl₃O₂) radicals (Brattin et al., 1985). Both trichloromethyl and its peroxy radical are capable of binding to proteins or lipids, or of abstracting a hydrogen atom from an unsaturated lipid, initiating lipid peroxidation and liver damage (Recknagel et al., 1989). Lots of studies indicate that natural substances from edible and medicinal plants exhibited strong antioxidant activity that could act against CCl₄-induced liver damage (Yeh et al., 2012, Yang et al., 2010, Desai et al., 2012, Sreelatha et al., 2008), because they contain lots of free radical scavenger such as phenolic acids and flavonoid compounds.

Bee pollen is the male seed of a flower blossom, collected by honey bees by adding sugars from nectar and secretion of honey bees to bind the grains together. It has been used as a health food supplement, even used as medicine for many years (Linskens and Jorde, 1997) due to its abundant nutrient properties including sugars, proteins, lipids, vitamins, carbohydrates and phenolic compounds (Campos et al., 2003). Phenolic compounds are one of the most critical ingredients related antioxidant activity in pollen. Usually, it contains vanillic acid, protocatechuic acid, gallic acid, p-coumaric acid, hesperidin, rutin, kaempferol, apigenin, luteolin, quercetin, and isorhamnetin (Chu et al., 2007, Bonvehí et al., 2001). This composition tends to be species-specific and be related to the therapeutic properties (antibiotic, antineoplasic, antidiarrhoeic and antioxidant) of pollen (Mărghitaş et al., 2009, Campos et al., 1997, Almaraz-Abarca et al., 2004). More specifically, the ingestion of bee pollen by rats has also been shown to decrease the level of the lipid oxidation products and increase the activities of antioxidant enzymes (Dudov and Starodub, 1994, Šarić et al., 2009).

Schisandra chinensis is widely distributed in China, and has been used as Chinese remedy for liver damage for several centuries. Many studies have reported that S. chinensis contains dibenzocyclooctadiene lignans, such as Schizarin A, B, C, D and E, and exhibits the function of hepatoprotective, antioxidant, anti-lipid peroxidative, anticancer and anti-HIV (Kuo et al., 2001, Chen et al., 2002, Chen et al., 1996, Yang et al., 1992, Zhang et al., 2009). Those studies mainly focus on the stem, root and seed of the vegetable. The bee pollen of S. chinensis, accounting for about 15% of total pollen production in China, has been sold as functional food in China for several decades. However, very little if any research has been done on the antioxidant activities of the pollen, especially undertaking on hepatoprotective effect on CCl₄-induced acute liver damage in rats.

The objectives of our study were: (1) to determine the total phenolic content (TPC), total flavonoid content (TFC) and individual phenolic compounds of S. chinensis pollen extract (SCPE); (2) and determine its free radical scavenging activity in vitro, reducing power and Ferrous ion-chelating activity; (3) to investigate the protective effects of SCPE on CCl₄-induced hepatic damage, including the effects of SCPE on the biochemical determinations of the levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and the levels of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) in liver homogenate combined with hepatic histopathological obervations in vivo.