Essential Oil from Fresh and Dry Leaves of Rosemary (Rosmarinus Officinalis L.): Antioxidant Activity and Microscopic Structure

Abstract

Rosemary ( Rosmarinus officinalis L.) is a medicinal plant from the Lamiaceae family, originally from the Mediterranean region and can be found in most parts of the world. Rosemary essential oil is central to medication, personal health care, cosmetic ingredients, spices, and food preservation with considerable biological activities. This research aimed to measure the oil yield of fresh and dry rosemary leaf samples, identify the chemical constituents of the oil, measure the antioxidant activity of the oil, and analyze the secretory cells of the leaves. These are important to support the development and deployment of rosemary essential oil. The method of drying leaf samples is essential for preserving the oil compounds and it influences both essential oil yield and antioxidant activity. Rosemary leaves were harvested from the field of Dasong Village, Sub-District of Sukasada, and the District of Buleleng, Bali, Indonesia. One part (5 kg) of the leaves samples was naturally dried at room temperature at natural atmospheric pressure for seven days and this was referred to shade drying. Another part of the leaf samples (5 kg) was freshly processed. Both shade-dried and freshly harvested rosemary leaves were extracted using steam distillation with three replications. The composition of the essential oils was determined using Gas Chromatography-Mass Spectrometry. Cross-sections of the leaves were prepared by the paraffin embedding method and stained with safranin. Leaf microscopic structure was observed under a light microscope. This study confirmed that the yields of essential oils from dry leaf samples were higher than fresh samples (0.56% and 0.36%, respectively). The oil from fresh and dry leaves contained 183 and 164 compounds respectively. The main constituents of both oils were eucalyptol, α-pinene, geraniol, linalool, and caryophyllene. The novelty of this study was that both oils from fresh and dry leaf samples have the same strong antioxidant activity with IC 50 of 83.08 ppm. This might be useful for the utilization of the oil for different purposes. The secretory structure of the essential oil was glandular trichomes of two types: peltate and capitate. Keywords: capitates glandular trichomes, essential oil, peltate glandular trichomes, Rosemarinus officinalis , steam distillation. https://doi.org/10.55463/issn.1674-2974.50.3.9