Analgesic, Anti-inflammatory, Acute Oral Toxicity and Phytochemical Study of Maerua Triphylla a. Rich. (Capparidaceae)

Abstract

Non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids, and opioids are used in the management of inflammation and pain. However, the use of these drugs is limited by cost, adverse effects, and the reappearance of symptoms after discontinuation. Given these limitations, the search for alternatives may be necessary. The roots of Maerua triphylla are used by Maasai and Kikuyu communities for the management of headaches, stomachaches, migraines, and rheumatism. However, data on the safety and efficacy of this plant is not available to support its use. The aim of this study was to investigate the safety (LD50), phytochemical constituents, analgesic, and anti-inflammatory properties of root extracts of M. triphylla. Cold maceration was used to prepare methanol and aqueous root extracts of M. triphylla. The safety of these extracts was evaluated in Wistar rats using the Organization for Economic Co-operation and Development (OECD 425) guidelines. Phytochemical composition of the extracts was determined by standard qualitative methods. The acetic acid-induced writhing procedure was used to evaluate the analgesic activity of the extracts in Swiss albino mice. The anti-inflammatory activity of the extracts was determined in Wistar rats using the acetic acid-induced paw oedema method. The percentage yield from the aqueous extraction was 12.4% whereas the percentage yield from the methanol extraction was 6.2%. All the studied plant extracts had LD50 > 2000mg/kg bw and were classified as nontoxic according to the OECD 425 guidelines. Qualitative phytochemical screening revealed the presence of flavonoids, phenols, cardiac glycosides and alkaloids in both extracts. However, saponins were only present in the methanol extract. In the analgesic study, mice that received 100 mg/kg bw and 500 mg/kg bw of aqueous root extract of M. triphylla had significantly lower acetic acid-induced writhing in comparison to mice that received 75 mg/kg bw acetylsalicylic acid (reference drug) (p< 0.05). Additionally, mice that received 500 mg/kg bw of methanol root extract of M. triphylla had significantly lower acetic acid-induced writhing in comparison to mice that received 75 mg/kg bw acetylsalicylic acid (p< 0.05). In the anti-inflammatory study, there was no significant difference (p>0.05) between the inhibitory activity of different doses of the aqueous root extract of M. triphylla and a 50 mg/kg dose of xv diclofenac sodium (reference drug) on acetic acid-induced paw edema in rats. Moreover, there was no significant difference in the inhibitory activity of 100 mg/kg bw and 500 mg/kg bw doses of the methanol root extract of M. triphylla and a 50 mg/kg dose of diclofenac sodium (p>0.05). These findings suggest that the roots of M. triphylla may be useful in the mitigation of pain and inflammation and therefore support their ethnomedicinal use in the management of inflammation and pain. Further isolation, characterization and quantification of the specific phytochemical constituents in the root extracts of M. triphylla with anti-inflammatory and analgesic activity is recommended. Furthermore, the specific mode(s) through which these extracts exert their reported pharmacological activities should be established. Further toxicological studies on the plant extracts are recommended to fully determine their safety.