Essential oil composition of Anacardium occidentale from Nigeria

Abstract

Anacardium occidentale L. (Anacardiaceae) is a multipurpose tree growing up to 8–10 m. It is native to the Amazon but is now dispersed in all tropical countries where it is cultivated [1]. The bark, fruit juice, and leaves of the tree are used medicinally, particularly in treating yaws and diarrhea, and the cashew nut has international appeal and market value as a food [1]. The fruit, apart from being delicious, is a richer source of vitamin C than oranges. The species is also esteemed as a reforestation species. Biological activities, including hypoglycemic [2], antimicrobial [3], molluscicidal [4], and leishmanial [5], has been reported for A. occidentale. The essential oil constituents of this plant growing in Brazil [6] and Malaysia [7] have also been investigated. The results of chemical analysis of the A. occidentale leaf essential oil are presented in Table 1. Sixty-five compounds, which represent 98.5% of total oil, were identified. The oil is composed mainly of monoterpenes (62.6%) and sesquiterpenes (31.1%). Non-terpenoid compounds account for 5.2% of the oil. Among the monoterpenes, the hydrocarbons are represented mainly by β-phellandrene (42.7%) and small amounts of α-pinene (4.3%), p-cymene (3.2%), trans-β-ocimene (3.1%), and α-phellandrene (2.0%) (Table 1). However, the content of oxygenated monoterpenes was smaller (4.8%), yielding α-terpineol (2.1%) as the main component. In the case of the sesquiterpenes, β-caryophyllene (4.4%) and germacrene D (4.0%) were the major hydrocarbons, while spathulenol (1.6%) and globulol (1.0%) occurred as the major oxygenated compounds in the oil. Considering similar oils found elsewhere, (E)-β-ocimene, α-copaene, and δ-cadinene predominated in the Brazilian leaf oil [8], while the flower oil consisted of a higher content of β-caryophyllene and a significant amount of methyl salicylate and benzyl tiglate, which were not present in leaf oil. All these compounds found in the Brazilian oil were present in relatively small quantities in the oil from Nigerian sample. The dominant compounds in cashew fruits were non-terpenoid compounds such as hydrocarbons, alcohols, aldehydes, and acids [6, 8, 9]. The monoterpene, trans-β-ocimene (76%), occurred as the chief constituent of Malaysian leaf oil [7] and may be responsible for the larvicidal and cytotoxicity activities reported for this plant. This compound was present in small proportion in the Nigerian leaf oil. Also, the predominant component of the Nigerian oil, β-phellandrene, was not detected in the oil from Malaysian samples. It is these three chemical varieties of A. occidentale leaf oil that are thus far recognized. Recently published results of the essential oil of A. occidentale leaf from Nigeria showed limonene as the dominant compound (85.9%) [10]. However, this compound was not detected in our sample.