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Pharmacognosy 1 Pharm 131 Course Teacher: Prof. Dr. Swarnali Islam Khandaker Lipids Lipids (fixed oils, fats, and waxes) are esters of long-chain fatty acids and alcohols, or of closely related derivatives. The chief difference between these substances is the type of alcohol; in fixed oils and fats, glycerol combines with the fatty acids; in waxes, the alcohol has a higher molecular weight, e.g., cetyl alcohol. Examples: @ Fixed oil: Olive oil, peanut oil ¢@ Fats: Lanolin, Theobroma oil, Lanolin @ Waxes: Beeswax, Jojoba oil » Fixed oils and fats differ only as to melting point; those that are liquid at normal temperatures are known as fixed oils, whereas those that are semisolid or solid at ordinary temperatures are known as fats. ¢@ Although most vegetable oils are liquid at ordinary temperatures and most animal fats are solid, there are notable exceptions, such as cocoa butter, which is a solid vegetable oil, and cod liver oil, which is a liquid animal fat. » The United States Pharmacopeia includes several tests that determine the identity, quality, and purity of fixed oils. Acid value or acid number Acid value or acid number is the number of milligrams of potassium hydroxide required to neutralize the free fatty acids contained in 1 g of the oil. e It indicates the amount of free fatty acids present in the oil. Saponification value Saponification value is the number of milligrams of potassium hydroxide required to neutralize the free fatty acids and saponify the esters contained in | g of the oil. e = Itindicates the amount of base that is needed to turn an oil into soap. 
