EXTRACTION OF ANTIOXIDANTS FROM MORINGA OLEIFERA LEAVES, STABILITY OF THE RESULTING ANTIOXIDANTS, AND USE OF THE REMAINING RESIDUE AS LIVESTOCK FEED

Abstract

Moringa oleifera, commonly known as horse radish tree or drumstick tree is a perennial multipurpose tropical tree. It can be used as medicine, cosmetic and functional food, among others. The benefits of using the leaves are ascribed to the presence of a number of antioxidants. Nowadays it is widely cultivated and naturalized in many countries. Simple methods to extract antioxidants from Moringa leaf are lacking, which were established, stability of antioxidants was assessed, and residue left after extraction was explored for use as animal feed, with the aim to scale-up the process to industrial scale. A natural source antioxidant-rich fraction prepared in this study could have applications in protecting against free radical mediated damage, to enhance shelf-life of products, and to prevent and/or cure diseases. Antioxidants are known to have anti-diabetic, antiinflammatory, anti-aging, cardio-and neuro-protective, intestinal microbiota regulatory effects, among others. The optimized procedure consisted of ultrasonication or extraction in a shaking water bath for 40 minutes at 30�C in 45% aq. ethanol at 1:10 (w/v) plant:solvent ratio. A high extraction yield by weight of 31-33% was obtained. The preparation was rich in antioxidants. On dry weight (DW) basis, total phenolics were from 19.6 to 33.5 mg catechin equivalents/g, FRAP (Ferric Reducing Antioxidant Power) from 83.3 to 140.7 nmol FeSO4 equivalents/g and DPPH (2,2-diphenyl-1-picrylhydrazyl) activity from 8.9 to 18.2 mg Trolox equivalents/g. The HPLC fingerprinting showed the presence of more than a dozen compounds, and the UV spectra were typical for flavonoids and phenolic acids, containing high amounts of chlorogenic acid and rutin. The antioxidants in a liquid state or after freezedrying were stable for over 3 months at room temperature, 4-6�C or - 18�C. The residue left after extraction had 42% crude protein and the essential amino acids contents were as high as that in soymeal. The residue can replace soymeal in dairy and beef cattle diets at 1:1 level by weight, and in fish diet at 30% replacement of fishmeal protein. This can decrease cost of animal feeding by 20-35%, giving higher profit to farmers and industry. Also, this residue is likely to provide health benefit to the animals being rich in catechin and kaempferol. The method developed is low-cost and easy to scale up, especially in a developing country settings. Good stability of the antioxidant preparation makes its attractive for use in cosmetic, pharmaceutical and food industries. It can also be a replacer of synthetic antioxidants in food and feed applications including ethoxyquin (used in fish feed), banned in many countries including the EU. The moringa antioxidant-rich fraction obtained in this study that corresponded to 1 g each of ascorbic acid, ethoxyquin or butylated hydroxytoluene (BHT) (all synthetic antioxidants) was 3.64 g, 4.3 g and 2.1 g, respectively. This antioxidant potential of moringa is very high, among other known oxidants isolated from plant parts. The study is an important step towards industrial scale development of isolating antioxidant-rich fraction and of incorporating the residue in animal diets, with zero waste � a vital requisite for circular economy.