Acute oral toxicity study of <i>Thymus serrulatus</i> and <i>Thymus schimperi</i> from Ethiopia

Abstract

Thymus serrulatus and Thymus schimperi both endemic to Ethiopia are used by the public as tea and food additives. They are claimed to have some sort of toxicity. However, no toxicity test has been conducted to date. So the present study aimed to test the acute oral toxicities of their Essential Oils (EOs). T. serrulatus was collected from Ofla (Ofl), Alamata (Ala), and Yilmana Densa (Yil) and T. schimperi from Tarmaber (Tar), Butajira (Buta), and Bale (Bal). The control group (Group I) mice were administered with calculated amounts of 0.1% Tween-80 in normal saline. Experimental group (Groups II to VI), on the other hand, were delivered with 2000 µL/Kg body weight of Ofl, Ala, Yil, Tar, Buta and Bal EOs respectively. Treated and control mice were observed, and changes were recorded for 14 days. On the 14 th day, after mice were humanely killed by heart puncture method, their organs were weighed, organ to body weight ratios were calculated and packed cell volumes (PCVs) were determined. Growth rate decrease was observed in mice treated with Yil and Buta EOs (carvacrol chemotypes) than in those treated with the thymol chemotypes (Ofl, Ala, Tar, and Bal). The organ to body weight ratios of the control group were either significantly higher than or comparable to that of the treatment groups implying that the EOs had no any inflammatory effects on the organs. The % PCVs of mice treated with the EOs were either significantly higher than or comparable to the control mice. The median lethal dose (LD50) of each EO was between 2000 µL/kg to 5000 µL/kg body weight. The LD50 values of the dry weights of thyme were calculated based on their EO yields that were approximated to be around 278g /kg bw (Bal), 313g /kg bw (Yil, Tar, and Buta) and 500g /kg bw (Ofl and Ala). Since the aerial parts, not the EOs, of thyme are used in the form of tea and food additives (not their EOs), this value is so high that these plants are not toxic. However, cautions should be taken for vulnerable groups.

Chemical Composition, Antioxidant Potential, and Blood Glucose Lowering Effect of Aqueous Extract and Essential Oil of Thymus Serrulatus Hochst. Ex Benth

“…The essential oil revealed a high amount of thymol therefore it can be classified as thymol chemotype oil ( Tirillini et al, 2008 ). This finding is in agreement with an earlier study which indicated that the essential oils of T. serrulatus belong to the thymol chemotype ( Asfaw et al, 2000 ; Tirillini et al, 2008 ; Damtie et al, 2017 ).…”

“…The essential oil of T. serrulatus is also used for medicinal purposes as antiseptic, antifungal, and vermifuge properties ( Asfaw et al, 2000 ). The bioactive potential of the plant is supported by previous experimental studies, which include antihelimenthic, antibacterial, fungicidal ( Damtie and Mokonen, 2015 ), diuretic ( Melka et al, 2016 ), vasodilatory ( Geleta et al, 2015 ), and hepatoprotective ( Damtie et al, 2017 ) activity.…”

“…of Semien Shoa, Tigray, and Wollo ( Damtie and Mekonnen, 2015 ; Melka et al, 2016 ). It is restricted to the northern parts of the country and is reported to be found in Alamata and Ofla (Tigray), Yilmana Densa (West Gojjam), and Tarmaber (North Shewa) ( Damtie et al, 2017 ). In turn, T. serrulatus is found in different parts of Ethiopia.…”

Phytochemical Constituents, Safety and Efficacy Study of Thymus schimperi and Thymus serrulatus

“…Saponins, flavonoids tannins and phytosterols were found in dichloromethane fraction of aqueous crude leaf extracts of T. serrulatus. n-butanol fraction of crude aqueous leaf extract of T. Serrulatus is composed of alkaloids, saponins, polyphenols, tannins and phytosterols which was comparable with the secondary metabolites of hexane, ethyl acetate, chloroform, butanol and methanol leaves extracts of T. vulgaris [33]. Aqueous and 80% methanol crude extract of T. schimperi leaves was qualitatively analyzed and the presence of steroids, alkaloids, flavonoids, saponins and tannins has been detected [34].…”

Possible Tracheal Relaxant and Antimicrobial Effects of the Essential Oil of Ethiopian Thyme Species (Thymus serrulatus Hochst. ex Benth.): A Multiple Mechanistic Approach

“…In Ethiopia, it is found in the northern highlands of Semien Shoa, Tigray, and Wollo areas ( Melka et al, 2016 , Damtie et al, 2018 ). It is known by the local communities as Tosign in Amhara and Tesni/Thasne in Tigray region of Ethiopia ( Damtie et al, 2017 ).…”