Chemical Characterization and Nutritional Markers of South African Moringa oleifera Seed Oils

Abstract

Moringa oleifera Lam (syn. M. ptreygosperma Gaertn.) leaves are globally acclaimed for their nutritional content and mitigation of malnutrition. In most impoverished rural communities including Limpopo, Mpumalanga and KwaZulu Natal of South Africa, powdered leaves of Moringa oleifera are applied as a nutritional supplement for readily available food such as porridge for malnourished children and even breast-feeding mothers. Widely practiced and admired is also the use of the plant seed in the do-it-yourself purification of water by rural South Africans. This study aimed at identifying the chemical and nutritional marker compounds present in South African Moringa oleifera seed oils using high resolution 1-2-dimension gas chromatography in order to give scientific validation to its uses in cosmetics and particularly in culinary practices. Results obtained from two-dimension tandem mass spectrometry chemical signature revealed over 250 compounds, five times more than those reported from one-dimension gas chromatography. Whereas previous reports from gas chromatography-mass spectrometry analysis reported oleic acid (70–78%) as the major compound from oil samples from other countries, M. oleifera seed oil from South Africa is marked by cis-13-octadeaconic acid with 78.62% and 41.9% as the predominant monounsaturated fatty acid in the hexane and dichloromethane extracts respectively. This was followed by cis-vaccenic acid, an isomer of oleic acid at 51% in the acetone extract, 9-octadecanoic acid-(z)-methyl ester at 39.18%, 21.34% and 10.06% in dichloromethane, hexane and acetone extracts respectively. However, a principal component analysis with R2 = 0.98 of the two-dimension tandem mass spectrometry cum chemometric analysis indicated n-hexadecanoic acid, oleic acid, 9-octadecanoic acid-(z)-methyl ester and cis-vaccenic acid with a probability of 0.96, 0.88, 0.80 and 0.79 respectively as the marker compounds that should be used for the quality control of moringa seed oils from South Africa. This study demonstrates that South African Moringa oleifera oils contain C-18 monounsaturated fatty acids similar to oils from Egypt (76.2%), Thailand (71.6%) and Pakistan (78.5%) just to mention but a few. These fatty acids are sunflower and olive oil type-compounds and therefore place moringa seed oil for consideration as a cooking oil amongst its other uses.