Castor oil (Ricinus communis): a review on the chemical composition and physicochemical properties
Ricinus communis is an annual oilseed crop commonly known as castor. It is sometimes called castor bean, but it’s not a true bean in nature. Castor plant, belonging to the spurge family Euphorbiaceae can grow in different geographical areas (Anjani, 2014). Growth of castor is favorable around 20 °C to 25 °C whereas temperatures lower than 12 °C or higher than 38 °C affects germination and yield (Severino et al., 2012; Yin et al., 2019). The plant growth and appearance vary greatly including its growth pattern, seed color and size, stem color and foliage, as well as oil content Figure 1 (Ramanjaneyulu et al., 2013; Sbihi et al., 2018). Castor seed is characterized by its elongated, ovoid, oval, or square shape; size variable, 0.5 to 1.5 cm long. Its seed color comprises a base color that varies from brown or red to black, brownish yellow, grey, and white Figure 1. The pattern as such ranges from fine to coarse vein-like or finely dotted to broad splotches (Naik, 2018; Salihu et al., 2014). The leaves change from pale green to dark red based on the content of anthocyanin pigmentation (Sbihi et al., 2018). The shape of the fruit is globe-like resembling a spiny capsule. The capsule which encloses the seeds cracks when fully matured Figure 1. Castor oil extracted from the seed mostly using n-hexane is very versatile Figure 1. Thus, it is utilized in several sectors such as agricultural, pharmaceutical, and industrial sectors. Products of castor oil include; ointments, nylon, varnishes, airplane engine lubricants, hydraulic fluids, dyes, detergents, plastics, synthetic leather, cosmetics, and perfumes (Anjani, 2014; Severino et al., 2012; Ying et al., 2017). Currently, castor oil production is predominant in India, China, and Brazil (Gad-Elkareem et al., 2019; Perdomo et al., 2013). The percentage of seed oil content ranges from 40 to 60% and the annual oil production is about 1.8 million tons worldwide (Perdomo et al., 2013). The chemistry of castor oil is based on the ricinoleic acid structure, carboxylic group, hydroxyl group, and the single point of unsaturation (Mubofu, 2016; Yusuf et al., 2015). These features provide additional strength to the oil structure. The fatty acid profiles present in castor oil are ricinoleic, oleic, stearic, palmitic, linoleic, linolenic acid and among others. Among them, ricinoleic acid, a monounsaturated fatty acid is the dominant acid constituting about 75 to 90% of the total oil composition (Beruk et al., 2018; Panhwar et al., 2016; Yusuf et al., 2015). It is worth saying that, the castor oil is the sole oil with such a high amount of fatty acid and this makes it unique from other vegetable oils. The fatty acid profile of castor Castor oil (Ricinus communis): a review on the chemical composition and physicochemical properties