The study was undertaken to evaluate the antioxidant activity of methanolic extract of Citrus limon seed. The extract was prepared by cold extraction in methanol and the methanolic extract was obtained by rotary evaporator. The extract was screened phytochemically. The antioxidant activity of methanolic extract of Citrus limon seed was studied by analysing Six different biochemical parameters which are indicative of antioxidant activity or potential of the extract. The studied biochemical parameters are DPPH radical scavenging activity, total flavonoid content, inhibitory action of the extract on lipid peroxidation, Ferric Reducing Activity Power (FRAP), total phenolic content, nitric oxide (NO) radical scavenging activity and Quercetin and Ascorbic acid were used as standard antioxidant respectively in the experiment.
Phytochemical screening result of methanolic extract of Citrus limon seed revealed the presence of phenol and flavonoid. The methanolic extract of Citrus limon seed has a higher percentage of DPPH radical scavenging activity at highest concentration of 400µg/ml with maximum activity of 45.29 1.006 compared with ascorbic acid standard and butylated hydroxylanisole that have the activity of 87.10 and 89.9 at the same concentration. Analysis of the plant extract revealed a high amount of flavonoids and phenol. The results of total flavonoid and total phenol content of Citus limon seed at 400µg/ml were 28.60 compared to ascorbic acid standard with the maximum activity of 42.12 0.2580 and 355.20 4.522 at the same concentration respectively .The methanolic extract of Citrus limon seed has the highest percentage inhibitory activity on lipid peroxidation of 60.31 0.6225 at the highest concentration 400µg/ml compared to ascorbic standard and quercetin standard with percentage of 84.030 0.1417 and 79.570 at the same concentration. The methanolic extract of Citrus limon seed has a highest percentage of FRAP activity and Nitric oxide content of 2.683 0.03032 and 125.4 at highest concentration of 400µg/ml compared to ascorbic standard with the activity of 2.831 0.02340 and 125.90 at the same concentration.
The work showed that methanolic extract of Citrus limon seed possess antioxidant active.
In living system,oxidation is a basic part of normal metabolic process, in which reactive oxygen species (hydrogen peroxide and hypochlorous acid) and many free radicals (hydroxyl radical (OH) and superoxide anion) are generated (Halliewell, 2000;Pietta, 2000;Vijayabaskaranet al., 2010). Rapid production of free radicals may cause alteration in the structure and function of cell constituents and membranes and can in human neurologic and other disorders such as cancer,diabetes,inflammatory disease,asthma,cardiovascular,neurodegenerative diseases and premature ageing. Therefore, the prevention of the above conditions requires the presence of antioxidants or free radicals scavenging molecules in the body.
There are plenty of antioxidant substances present in plants (fruits, vegetables, medicinal herbs, etc.) and the free radical scavenging molecules present in them are in the form of phenolic compounds (e.g.phenolic acids,flavonoids,quinines, coumarins,lignans,tannins), nitrogen compounds (alkaloids, amines), vitamins, terpenoids (including carotenoids), and some other endogenous metabolites. So to maintain a healthy body, one should always increase the intake of foods rich in antioxidant compounds that lower the risk of chronic health problems associated with the above disease conditions (Halliwell, 1994; Klipsteinet al., 2000;Bimal et al., 2011). Naturally occurring antioxidants can be used in foods and also for prevention and treatment of free radical-related disorders which can also be replaced by commercially available,synthetic antioxidants such as butylatedhydroxyanisole (BHA) and butylatedhydroxytoluene (BHT), which are quite unsafe to use and is restricted due to their carcinogenic effects. Nitric oxide (NO) is a potent pleiotropic inhibitor of platelet aggregation and 16 regulation of cell mediated toxicity. It is a diffusible free radical that plays many roles as an effectors molecule in diverse biological systems including neuronal messenger, vasodilation and antimicrobial activities. The most commonly used methods for measuring antioxidant activity are those which involve the generation of free radicals which are then neutralized by antioxidant compounds. DPPH is a well-known radical and a trap (scavenger) for other radicals (Husain et al., 1987, Visioliet al., 2000;Parr et al., 2004;Solaiet al., 2010).
Antioxidants in all leaves play important roles as health protecting factors due to the fact that they are unable to neutralize reactive oxygen species (ROS) and thus prevent a condition known as oxidative stress. Important nutraceutical agents are phenolic compounds which are crucial for their activity as antioxidants.The nutritive value of seed is not considered as its ability to supply the basic nutrients such as carbohydrates, protein and lipids, but also its ability to provide other health benefits (Oboh, 2006). These health benefits are contributed by the presence of certain bioactive phytochemicals in the leaves materials. In recent times, a lot of focus have been shifted to functional food research in order to identify and characterize the various nutraceutical agents in various types of food and for them to be applied for their various health benefits such as reduction of risk towards specific diseases, or maintenance and treatment for given health condition (Oboh, 2006).
By definition, ´traditional´ use of herbal medicines implies substantial historical use, and this is certainly true for many products that are available as ´traditional herbal medicines´. Traditional herbal medicine is sometimes referred to as alternative medicine. It is the indigenous healing system based on the culture, traditional of the people with their beliefs about the causes or ill-health, According to the World Health Organisation (WHO) (1978), Traditional medicine is the sum total of all knowledge and practices whether explicable or not used in the diagnosis, prevention and elimination of physical, mental imbalance and relying exclusively on practical experience and observation down from generation whether verbally or in writing depending on the religious and socio-cultural beliefs. It is a practice derived from the values and perception of the members of the community.The pharmacological treatment of disease began long ago with the use of herbs (Schulz et al., 2001).