Asian Research Thesis Index

Abstract

In the present work, the seeds of six local varieties (CIM-496, N-121, Z-33, AA-802, Desi, and CIM-534) of cotton (Gossypium hirsutum L.) harvested from three different provenances of Punjab (Bahawalpur, Bahawalnagar and Rahim Yar Khan districts) were investigated to characterize and compare their proximate composition as well as physicochemical and antioxidant characteristics. The amount of oil and protein in the tested seeds varied from 13.11 to 18.35% and 20.13-28.04%, respectively, revealing significant (p< 0.05) differences among varieties analyzed. While the contents of fiber (20.29-21.53%), ash (3.45-5.08%) and moisture (6.36-8.44%) did not vary notably. The physicochemical properties includingdensity (24 ºC) 0.9019-0.9208 (g mL-1), refractive index (40 °C) 1.4601-1.4632, saponification value 177.01-190.28 (mg of KOH/g of oil), free fatty acids 3.35-4.41%, iodine value 100.54-109.54 (mg KOH/g oil), unsaponifiable matter 0.49-0.58% (w/w) , and color (1-in.cell) 12.01-13.04 R + 63.61-68.11Y of the extracted cottonseed oils (CSOs) were recorded. The oxidation parameters of CSOs, as assessed by estimation of conjugated dienes, conjugated trienes, peroxide value, para-anisidine and induction period (Rancimat, 20 L h-1, 120 °C), were noted to be 2.11 to 2.61, 0.91-0.99 , 1.71-2.07 (meq kg-1 of oil), 2.00-2.31and 3.19-3.62 h, respectively. The CSOs were found to contain mainly linoleic acid (48.94 to 50.46%), followed by palmitic acid (24.42-25.86%), oleic acid (17.81-23.15%) and stearic acid (2.49-2.81%). The contents of α, γ and δ tocopherols in the CSOs were 125.47-296.20, 195.20-364.25 and 2.10-5.81 (mg kg-1), respectively. Total phenolic contents (TPC) and DPPH radical scavenging capacity of CSOs was recorded to be 1.32-0.94 (mg GAE/100g of dry matter) and IC50-1.00-2.18 (µg mL-1), respectively. A number of physicochemical and antioxidant parameters of the tested oils varied significantly (p<0.05) among the varieties analyzed that might be attributed to agro climatic variations and the genetic makeup of the cotton plants. 	Moreover, different solvent extracts produced from defatted cotton seeds (oilseed residues) were evaluated for antioxidant attributes in terms of measurements of TPC (0.94-3.80 mg GAE/100g), total flavonoids (TF) (0.62-2.45 CE mg/100g), DPPH radical scavenging capacity (IC50) (1.03-2.15 µg mL-1), percent inhibition of linoleic acid peroxidation (39.82-88.05%) and reducing potential (0.14-0.48 mg mL-1). These data demonstrated the defatted cotton seeds to be a potential source of natural antioxidants. Generally, the aqueous alcoholic extracts of the oilseed residues exhibited superior antioxidant activity and phenolic amounts advocating the selection of these extraction solvents for optimum recovery of cottonseed antioxidants. The results of the present analytical study can be helpful to select appropriate cotton varieties for harvesting under local agroclimatic conditions so as to explore their functional food and nutraceutical applications.

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