Antioxidant Properties and Chemical Composition of Lavandula tenuisecta , An Endemic Species of Morocco
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ANTIOXIDANT PROPERTIES AND CHEMICAL COMPOSITION OF Lavandula tenuisecta, AN ENDEMIC SPECIES OF MOROCCO
A. Sayout, A. Ouarhach, and A. Romane*
Lavandula tenuisecta Coss. ex Ball (Lamiaceae) is an endemic species of Morocco [1]. The chemical composition of Lavandula tenuisecta has never been described in the literature. Therefore, to justify its different uses in traditional medicine, determination of the chemical composition of L. tenuisecta is a necessary step. The aerial part of L. tenuisecta was harvested manually during the flowering period in the mountains of the High Atlas of Morocco, Agdez and Ouarzazate (altitude 1516 m, latitude (N) 30°43.943′, longitude 006°39.353) and identified by Prof. Ahmed Ouhammou (Cadi Ayyad University). The specimen was deposited in the Herbarium of Cadi Ayyad University in Marrakech (Mark 8449). The three parts of the plant (flowers, stems, and leaves) were separated, and the essential oil from each part was extracted using the hydrodistillation method. The yields of essential oils obtained for this plant are 0.01% (v/w, flowers), 0.02% (v/w, leaves), and 0.07% (v/w, stems). Chromatographic analysis of its essential oils was carried out by GC/FID and GC/MS [2]. The results show that all parts of L. tenuisecta were poor in essential oils (Table 1). Analysis of the oils allowed the identification of more than 88.6% of the volatile compounds, representing a total of 38 compounds. This analysis showed that the essential oils are rich in oxygenated monoterpenes (79.2–86.2%), followed by hydrocarbon monoterpenes (3.9–5.3%), and oxygenated sesquiterpenes (1.6–3.3%). The majority of essential oils extracted from Lavandula species have chemical compositions frequently described in the literature [3–5]. On the other hand, the essential oil of L. tenuisecta has a different composition, characterized by the presence of camphor (20.9–26.4%), 1,8-cineol (19.4–38.1%), and fenchone (16.0–22.0%) as major compounds. The GC/MS and GC/FID results (Table 1) showed the absence of carvacrol, which was predominant in L. coronopifolia [6]. Knowing that the main compounds of different parts of L. tenuisecta have different medicinal properties [7], this rare species may, therefore, be considered as a new source of drugs. The antioxidant potential of different parts was evaluated using the scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing power assays (FRAP) [8, 9]. The inhibitory concentration IC50 and the effective concentration EC50 were determined, successively, from the DPPH inhibition and FRAP curves (Table 2). A low IC50 or EC50 value corresponds to a high antioxidant activity. Comparing the antioxidant activities of the parts of Lavandula tenuisecta, the essential oil of the flowers was more active (IC50 2.15 ± 0.09 mg/mL and EC 50 2.27 ± 0.06 mg/mL) than that of the leaves (IC50 3.01 ± 0.10 mg/mL and EC50 2.85 ± 0.12 mg/mL) and stems (IC50 11.50 ± 0.18 mg/mL and EC50 9.15 ± 0.09 mg/mL). These activities are weak compared to ascorbic acid (IC50 0.11 ± 0.01 mg/mL and EC50 0.42 ±
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