ABSTRACT
Caralluma arabica N. E. Br. (Milkweed family: Asclepeadaceae) is commonly known as ‘gems of the hills’ in English, khanasoor or khanaseer in Arabic. The origins of the genus Caralluma are derived from the Arabic word qarh al-luhum,meaning wound in the flesh or abscess [1]. It is a perennial, stem-succulent shrub, often found in large clumps of stems up to30 cm high, that grows in mountainous areas in rocky habitats. It is found with purple or brown–gray top flowers. The Northern regions of Oman have been blessed with an abundance of Caralluma flava, Caralluma arabica, and Caralluma penicillata as these prefer the limestone habitat [2]. Certain species of Caralluma are used in folk medicine asantidiabetic, anti-ulcer, antibacterial, antipyretic, and antirheumatic, and have been reported to possess significant anti-inflammatory activity [1, 3–6]. Throughout history, traditional uses of the Caralluma species have been documented in Arabic and Indian traditional medicine. Caralluma arabica was specifically reported in treating cardiovascular diseases [7]and skin infections [8]. It is also native to Ibri, Oman and has been shown to be a rich source of a wide range of phytochemicals, including alkaloids, pregnanes, flavonoids, triterpenes, saponins, etc. [1].It is used in traditional medicine as a decoction in the United Arab Emirates (UAE) for the treatment of manydisease conditions. To the best of our knowledge, this is the first report on the chemical composition of essential oil of Caralluma arabica growing in Oman. We also investigated its useful biological activities such as antibacterial, anti-oxidant and hemolytic activities to validate its traditional uses.
The essential oil from the whole plant Caralluma arabica (voucher specimen number: COP/PHAR425/2019/02) washydrodistilled for 6 h with the help of a Clevenger apparatus following a previously reported method [9]. A greenish yellow oil was obtained in a yield of 0.5% (v/w), which was dried over anhydrous sodium sulfate. GC-MS analysis of the extracted Caralluma arabica essential oil (CAEO) identified 48 known chemical compounds after matching their mass spectra with database (NIST, Wiley MS library) representing 87.98% of the total oil (Table 1). Nearly half of the identified volatile constituents belong to the monoterpenoids (29.29%) and sesquiterpenoids (21.22%) class of compounds whereas monoterpenes and sesquiterpenes accounted for only 34.3%. CAEO was also found to contain methoxylated phenolic derivative, ester of benzyl alcohol, and a saturated fatty acid in small amounts (<1%). β-Selinenol, a sesquiterpenoid, was identified as the majorchemical constituent followed by patchoulane (8.89%), δ-selinene (6.18%), L-pinocarveol (4.96%), L-verbenone (4.63%),and β-elemene (4.52%). Other bioactive volatile constituents of pharmaceutical significance including bornyl acetate,α-pinene, limonene, trans-verbenol, α-terpineneol, α-terpinyl acetate, m-cymenol, β-bourbon Ene, α-selinene, δ-cadinene,elemol, and cadinol, were also detected in minor quantities (> 1–4%). When we compare our results with essential oil from flowers of Caralluma europaea, it can be seen that its major compounds are monoterpenoids viz., linalool – 18.4%,α-terpinene – 19.1%, and terpinolene – 23.3%) [10]