Leaf methanol extract of C. orbiculata L. was investigated for antinociceptive and anti-inflammatory activities using acetic acid writhing and hot-plate tests and carrageenan-induced oedema test in mice and rats, respectively. C. orbiculata (100–400？mg/kg, i.p.) significantly inhibited acetic acid-induced writhing and significantly delayed the reaction time of mice to the hot-plate-induced thermal stimulation. Paracetamol (300？mg/kg, i.p.) significantly inhibited the acetic acid-induced writhing in mice. Morphine (10？mg/kg, i.p.) significantly delayed the reaction time of mice to the thermal stimulation produced with hot plate. Leaf methanol extract of C. orbiculata (50–400？mg/kg, i.p.) significantly attenuated the carrageenan-induced rat paw oedema. Indomethacin (10？mg/kg, p.o.) also significantly attenuated the carrageenan-induced rat paw oedema. The LD50 value obtained for the plant species was greater than 4000？mg/kg (p.o.). The data obtained indicate that C. orbiculata has antinociceptive and anti-inflammatory activities, justifying the folklore use of the plant species by traditional medicine practitioners in the treatment of painful and inflammatory conditions. The relatively high LD50 obtained shows that C. orbiculata may be safe in or nontoxic to mice. 1. Introduction Pain and inflammation are some of the most common manifestations of many diseases afflicting millions of people worldwide [1, 2]. Even though there are effective orthodox medicines used to alleviate these manifestations [3], traditional medicine practitioners in, mainly, developing countries have used herbal medicines to treat various ailments including pain and inflammation [4]. The dependence of the population especially in the rural communities in South Africa on plant medicines as well as traditional medicine practitioners for their healthcare needs is cultural. One of such plants used by traditional medicine practitioners to treat various ailments is Cotyledon orbiculata L. [5, 6]. It belongs to the family Crassulaceae. It is a small shrub with fleshy leaves and widely distributed in Southern Africa. It is known locally as “Seredile” in Sotho and Tswana, “Plakkie” in Afrikaans, and “Imphewula” in Xhosa [5, 6]. C. orbiculata is used in the treatment of various ailments in different parts of South Africa. The fleshy leaves have been used to treat corn and warts. The juice of the leaves is used as drops for earache and toothache and as hot poultice for boils and inflammation [5–7]. Infusion of the fleshy leaves of C. orbiculata has also been used by traditional medicines
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