Extraction, Derivatization, Characterization and Antifungal Investigation of Limonene from Citrus sinensis Peels

Abstract

Limonene, a cyclic monoterpene is the main component in citrus oils. Oranges (Citrus sinensis) were sourced from a local market, peeled and the peels collected for this study. The orange peels were distilled using steam distillation to obtain the oil. The oil obtained was then distilled to obtain a pure colourless form of limonene (95%). The limonene (2 ml) was dissolved in dry chloroform (25 ml) and freshly distilled hydroiodic acid (57%; boiling point 127 °C) to give the derivative iodo-limonene (1.4 g; 30% yield). Another reaction of epoxidation of limonene was carried out by reacting limonene with hydrogen peroxide and acetic acid to give limonene epoxide (2.3 g; 36% yield). FT–IR analyses and GC-MS analyses were carried out to confirm the properties of the limonene. Antifungal tests on limonene against two fungi: Trichoderma harzianum (T. harzianum) and Marcophomina phaseolina (M. phaseolina) were carried out using poisoned food technique. 9 ml of potato dextrose agar (PDA) and 1 ml of limonene extract were used on both fungi. Petri dishes of agar without limonene served as control. Biological activities of the species were: T. harzianum culture 1 day 1-4: 0.00 mm ≡ no growth, day 5:1.5 mm → slight growth; T. harzianum culture 2 day 1–5: 0.00 mm ≡ no growth; M. phaseolina culture 1 days 1–4: 0.00 mm ≡ no growth, day 5:1.5 mm; M. phaseolina culture 2 days 1–3: 0.00 mm ≡ no growth, day 4: 1.50 mm → slight growth, day 5: 2.10 mm progressive growth. Results showed that both fungi were active in all media. Percentage inhibition of limonene against both fungal species using 1 ml of limonene was 95% for T. harzianum and 89% for M. phaseolina.

Keywords: Limonene; Extraction; Characterization; Antifungal; Epoxide.