Castor oil (Ricinus communis): a review on the chemical composition and physicochemical properties

Abstract Increasing world population has markedly increased the demand for vegetable oils for domestic and industrial purposes. Plant-based vegetable oils have been identified as one of the oils with high nutritive value. Castor plant is one of the oilseed with rich oil content owing to its high monounsaturated fatty acid and bioactive compounds. Its fatty acid profile constitutes mainly of ricinoleic acid and other minor acids such as stearic, palmitic, and oleic acid. Ricinoleic acid of castor oil is unique among all other vegetable oils, making it attractive for a wide spectrum of applications. The predominant triglyceride component in the oil is triricinolein. Minor biological compounds including carotenoid, tocopherol, tocotrienol, phytosterol, phospholipid, phytochemical, and phenolic compounds are present in castor oil. These compounds offer oxidation stability, anti-inflammatory, and antioxidant properties to the oil. The acid, anisidine, iodine, viscosity, and saponification values indicate that castor has good oil quality compared to other vegetable oils. Castor oil composition is influenced by the area of production and method of extraction adopted. The chemical structure of castor oil is centered on the ricinoleic acid and three major functional groups linked by glycerol moiety. More research on the oil’s component is being investigated nevertheless efficient and eco-friendly extraction methods are required. This review, therefore, summarizes the castor oil composition namely the triglyceride, various fatty acids and bioactive compounds, extraction methods, as well as its physicochemical properties.摘要 全球人口的持续增长显著提升了家用及工业领域对植物油（vegetable oils）的需求。植物基植物油（Plant-based vegetable oils）被认定为一类具备高营养价值的油脂。蓖麻作为油料作物（oilseed）之一，因富含单不饱和脂肪酸（monounsaturated fatty acid）与生物活性化合物（bioactive compounds），其含油量颇高。其脂肪酸组成（fatty acid profile）主要包含蓖麻酸（ricinoleic acid），以及硬脂酸（stearic acid）、棕榈酸（palmitic acid）、油酸（oleic acid）等少量脂肪酸。蓖麻油中的蓖麻酸在所有植物油中独具特性，使其拥有广泛的应用场景。该油脂中的主要甘油三酯组分（triglyceride component）为三蓖麻酸甘油酯（triricinolein）。蓖麻油中还含有类胡萝卜素（carotenoid）、生育酚（tocopherol）、生育三烯酚（tocotrienol）、植物甾醇（phytosterol）、磷脂（phospholipid）、植物化学物质（phytochemical）与酚类化合物（phenolic compounds）等微量生物活性成分。这些成分赋予蓖麻油氧化稳定性（oxidation stability）、抗炎活性与抗氧化特性（antioxidant properties）。通过酸值（acid value）、茴香胺值（anisidine value）、碘值（iodine value）、黏度（viscosity）与皂化值（saponification value）的检测结果可知，相较于其他植物油，蓖麻油具备优良的油品品质。蓖麻油的组成会受种植区域与采用的提取方法（extraction methods）影响。蓖麻油的化学结构以蓖麻酸为核心，由甘油骨架（glycerol moiety）连接三大主要官能团。目前学界正对该油脂的成分开展更多研究，但仍需开发高效且环保的提取方法。本综述旨在总结蓖麻油的组成成分——包括甘油三酯、各类脂肪酸与生物活性化合物、提取方法，以及其理化性质（physicochemical properties）。