Antioxidant activity and total phenolic content of ethanolic extract of Caesalpinia bonducella seeds

Abstract

The aim of this study was to assess the in vitro potential of ethanolic extract of Caesalpinia bonducella seeds as a natural antioxidant. The DPPH activity of the extract (20, 40, 50, 100 and 200 μg/ml) was increased in a dose dependent manner, which was found in the range of 38.93–74.77% as compared to ascorbic acid (64.26–82.58%). The IC₅₀ values of ethanolic extract and ascorbic acid in DPPH radical scavenging assay were obtained to be 74.73 and 26.68 μg/ml, respectively. The ethanolic extract was also found to scavenge the superoxide generated by EDTA/NBT system. Measurement of total phenolic content of the ethanolic extract of C. bonducella was achieved using Folin–Ciocalteau reagent containing 62.50 mg/g of phenolic content, which was found significantly higher when compared to reference standard gallic acid. The ethanolic extract also inhibited the hydroxyl radical, nitric oxide, superoxide anions with IC₅₀ values of 109.85, 102.65 and 89.84 μg/ml, respectively. However, the IC₅₀ values for the standard ascorbic acid were noted to be 70.79, 65.98 and 36.68 μg/ml respectively. The results obtained in this study clearly indicate that C. bonducella has a significant potential to use as a natural antioxidant agent.

Introduction

Oxidation is essential to many living organisms for the production of energy to fuel biological processes. However, oxygen-centred free radicals and other reactive oxygen species (ROS), which are continuously, produced in vivo, result in cell death and tissue damage. The role of oxygen radicals has been implicated in several diseases, including cancer, diabetes and cardiovascular diseases, ageing, etc. (Halliwell and Gutteridge, 1999). Antioxidants are vital substances which possess the ability to protect the body from damage caused by free radical induced oxidative stress (Ozsoy et al., 2008). There is an increasing interest in natural antioxidants, e.g., polyphenols, present in medicinal and dietary plants, which might help prevent oxidative damage (Silva et al., 2005). Polyphenols possess ideal structural chemistry for free radical-scavenging activity, and they have been shown to be more effective antioxidants in vitro than tocopherols and ascorbate. Antioxidant properties of polyphenols arise from their high reactivity as hydrogen or electron donors, and from the ability of the polyphenol derived radical to stabilise and delocalise the unpaired electron (chain-breaking function), and from their ability to chelate transition metal ions (Rice-Evans et al., 1997).

Human body has multiple mechanisms especially enzymatic and non enzymatic antioxidant systems to protect the cellular molecules against reactive oxygen species (ROS) induced damage (Anderson, 1999). However the innate defense may not be enough for severe or continued oxidative stress. Hence, certain amounts of exogenous antioxidants are constantly required to maintain an adequate level of antioxidants in order to balance the ROS in human body. Many synthetic antioxidants such as butylated hydroxyl anisole (BHA) and butylated hydroxyl toluene (BHT) are very effective and are used for industrial processing but they possess some side effects and toxic properties to human health (Anagnostopoulou et al., 2006). Hence, compounds especially from natural sources capable of protecting against ROS mediated damage may have potential application in prevention and/or curing of diseases.

The phenolic compounds in herbs act as antioxidants due to their redox properties, allowing them to act as reducing agents, hydrogen donors, free radical quenchers and metal chelators (Javanraedi et al., 2003).

Among the various medicinal and culinary herbs, some endemic species are of particular interest because they may be used for the production of raw materials or preparations containing phytochemicals with significant antioxidant capacities and health benefits (Exarchou et al., 2002). Crude extracts of fruits, herbs, vegetables, cereals and other plant materials rich in phenolics are increasingly of interest in the food industry because they retard oxidative degradation of lipids and thereby improve the quality and nutritional value of food (Javanraedi et al., 2003).

Researchers have studied polyphenolic constituents of various legume seeds and have reported that they contain potential medicinal/nutraceutical properties including antioxidant activities (Siddhuraju, 2006). Therefore the study of the importance and role of non-nutrient compounds particularly phenolic acids, flavonoids and high molecular tannins of legumes as natural antioxidants have greatly increased (Siddhuraju and Becker, 2007).

Caesalpinia bonducella F., (Caesalpiniaceae) commonly known as Nata Karanja, a prickly shrub found throughout the hotter parts of India, and Sri Lanka, has grey, hard, globular shaped seeds with a smooth shining surface. Seeds consist of a thick, brittle shell with a yellowish white bitter fatty kernel (Nadkarni, 1954). Plant is reported to have multiple therapeutic properties like antipyretic, antidiuretic, anthelmintic and antibacterial, anti-anaphylactic, antidiarrheal, antiviral (Dhar et al., 1968), antiasthmatic, antiamebic and anti-estrogenic (Raghunathan and Mitra, 1982). However, no reports are available on the antioxidant activity of C. bonducella seeds, therefore present investigation was undertaken to examine the total phenolic content and antioxidant activities of ethanolic extracts of C. bonducella seeds (CESE) through various in vitro models. Possible relationship between phenolic content and antioxidant activity was also seen.