Pages: (13-23 )
Abstract
The family Cucurbitaceae consisting of many economic plants (squashes, melons, cucumber, pumpkins, luffas, and watermelons) is faced with the problem of proper classification based on the use of few morphological characters. There is therefore the need to employ many more taxonomical characters to give a broad based classification using seed-oil characters. The objectives of the study were to identify and determine the physical properties of seed-oils; elucidate taxonomic Relationships through numerical analysis of these oils in the selected species of the family. Seeds from fourteen species of Cucurbitaceae were collected from various locations in Osun and Kwara States, Nigeria and were identified in the Forestry Herbarium, Ibadan and Herbaria of Universities of Ibadan and Ilorin. Two grams of oil were extracted from the seeds of each species with Soxhlet extractor using Petroleum ether at 60- 80°C. The physicochemical properties of the samples were investigated using Standard Procedures of Association of Official Analytical Chemists while the fatty acid compositions were determined using Gas Chromatography 7890 and Mass Spectrophotometer VL 597SC and Injector 7683B. The pH values, Specific gravity, and refractive index value ranged from 5.02-6.80, 0.87-0.96 and 1.46-1.48 respectively. The Acid, Iodine, and Peroxide values ranged from 1.21-18.16mgKOH/g, 0.62-126.40 and 1.26-18.74mg/g respectively. The Saponification values were between 115.92 and 210.52mgKOH/g except for Lagenaria siceraria (flask shaped), L. siceraria (spherical) and L. cylindrica which had saponification values of 22.08 mgKO H/g, 66.77mgKOH/g and 66.81 mgKOH/g respectively. Significant differences (p≤0.05) existed among the species based on physicochemical analysis. Seed-oil characters complemented morphological features in identification of varieties and species in the family. The study concluded that seed-oils were found to be good taxonomic characters and are recommended for use in solving problem of classification in the family Cucurbitaceae.
Keywords: Taxonomy, Morphological characters, Herbarium, Saponification, seed oil,