Determination of fatty acids and physicochemical properties of neem (Azadrachta indica L) seed oil extracts

Abstract

Neem tree is a folklore plant mostly used in medicinal preparations. Therefore, neem seeds were investigated with the aim of determining its fatty acid composition and physicochemical properties of the oil extract. The oil was extracted from the powdered seed using n-hexane with the help of Soxhlet which yielded 29.71% oil. Results revealed that the oil was liquid at room temperature and physically stable at varying temperatures (0, 50 and 100°C). It appeared to be pale greenish yellow, garlic-like odour, had a little bitter taste, viscosity of 12.2Pas and pH value of 6.78 ± 0.0135. The chemical parameters were identified to be 1.22 ± 0.029%, 2.36 ± 0.054 mg NaOH/g oil, 172.84 ± 0.559 mgNaOH/g oil and 1.88 ± 0.059 meq/kg oil for free fatty acids, acid value, saponification value and peroxide value respectively. The GC-MS analysis showed that the oil extract contained six different fatty acids with total composition of 63.07% oil. The compound with the highest composition was linoleic acid (40%) followed by oleic (35%), cis-13-octadecenoic acid (8.9%), palmitic acid (8.5%), stearic acid (7.5%) while the least compound was cis-vaccenic acid (0.5%). However, contrary to previous work where it was reported that oleic acid or linoleic acid was the dominant fatty acid found in neem oil. Linoleic acid was found to be dominant in this current research work. It is however recommended that under-utilized neem seeds should be explored the more with a view to producing viable products.