br Introduction Ocimum basilicum O basilicum

Introduction Ocimum basilicum (O. basilicum) Linn., popularly known as sweet basil in English, “Tulsi” in Hindi and “Raihan” in Arabic, belongs to the family Lamiaceae. It is an annual herb that is widely grown as a commercial ornamental crop in tropical and warm temperate regions of the world including Asia, Africa, Central and South America (Sajjadi, 2006; Hossain et al., 2010). Basil is an erect branching herb that grows 0.3–1.3 m high, with light green silky leaves. Its leaves are simple, opposite, 3–11 cm long, 1–6 cm wide, ovate, acute and usually toothed containing numerous oil glands which store essential oils (Kathirvel and Ravi, 2012). The flowers of sweet basil are white to purple in color and arranged in a terminal spike (Daneshian et al., 2009). Omani basil can be distinguished from other cultivars of basil based on its height and different look (Hanif et al., 2011). Aroma in spices is the result of complex mixtures of volatile substances, such as terpenes, sesquiterpenes, oxygenated derivatives and phenyl propanoids. The volatile fraction is designated as“essential oils” (Dýaz-Maroto et al., 2002). These substances can be extracted by different methods: hydrodistillation, extraction with organic solvent and supercritical fluid extraction (SFE) (Filip et al., 2014). Among these methods, hydrodistillation has been the most common approach to extract the essential oils from the medicine herbs and plants (Chinese Pharmacopoeia Committee, 2010). Alternative methods, employing microwaves, have been developed in order to shorten extraction time, improve the extraction yield, and reduce the operational costs. Microwave-assisted procedures for isolating essential oils have become attractive for use in laboratories and industry. The advantages of using microwave ARCA for oil extraction are more effective heating, fast energy transfer, faster response to process heating control, faster start-up, increased production, and elimination of some process steps. Novel microwave-assisted extraction (MAE) (Kaufmann and Christen, 2002) methods such as microwave-assisted hydrodistillation (MAHD) (Golmakani and Rezaei, 2008a, 2008b; Wang et al., 2010; Kusuma and Mahfud, 2016) and solvent-free microwave extraction (SFME) (Filly et al., 2014) have proven to be fast and efficient methods for extracting essential oils from medicinal plants. However, to the best of authors\' knowledge no work has been published on the extraction of essential oil from O. basilicum using microwave ovens for heating. Therefore, the objective of this study was to investigate the potential of MAHD and SFME for the extraction of essential oils from O. basilicum. In this study, the author also attempted to know and verify the kinetics and mechanism of MAHD and SFME of O. basilicum based on second-order model.
Materials and methods
Results and discussion
Conclusion The extraction yield of basil oil obtained by MAHD method for 160 min and SFME method for 60 min is 0.78%. Kinetics of oil extraction from basil (O. basilicum) by MAHD and SFME methods proved that the extraction process was based on the second-order extraction model as the experimentally done in three different steps. The initial extraction rate, h, was 0.0305 g L−1 min−1 for MAHD method and 0.1702 g L−1 min−1 for SFME method, the extraction capacity, CS, was 0.8371 g L−1 for MAHD method and 0.8229 g L−1 for SFME method, the second-order extraction rate constant, k, was 0.0436 L g−1 min−1 for MAHD method and 0.2513 L g−1 min−1 for SFME method and coefficient of determination, R2, was 0.9355 for MAHD method and 0.9842 for SFME method.