Pain, the commonest symptom which patients complain about, is a sensory and perceptual occurrence which causes suffering and emotive state of risks associated with anxiety and warns against body damage in order to protect against injuries and maintain survival (Swieboda et al., 2013). It has been theorized that all forms of pain are caused by inflammation (Omoigui, 2007). Thus, it is better to develop analgesics drugs which also possess anti-inflammatory effect.

Morinda lucida, an evergreen medium size tropical tree which grows up to 15 m in height with scaly grey twisted branches/stems (Igwe et al., 2009), is one of the many medicinal plants utilized as a remedy for pain and inflammation in folkloric medicine. It is also used to treat many other diseases such as malaria, yellow fevers, dysentery and leprosy (Iwu and Anyanwu, 1982). The plant is a source of diverse classes of chemical constitutes such as alkaloids, flavonoids, anthraquinones and iridoids (Lawal et al., 2012; Ogunlana et al., 2008).

Iridoids are cyclopenta [c]pyran monoterpenoids classes of secondary metabolites found in both plants and animals. Structurally, the iridoids skeleton consist of a six-membered ring encompassing an oxygen atom connected to a cyclopentane ring (Viljoen et al., 2012) with a variety of substitutions in existence. Iridoids are known to possessed anti-inflammatory, anti-neoplastic, cardioprotective, anti-protozoan, anti-leishmania, anti-trypanosomal and anti-hypoglycemic activities just to mention a few [(Abdel-Kader and Alqasoumi, 2021; Alkhaldi et al., 2020; Hien et al., 2018; Nguyen et al., 2005).

In recent years, two novel tetracyclic iridoids were isolated from the leaf of M. lucida which demonstrated profound anti-trypanosomal activity (Kwofie et al., 2016; Suzuki et al., 2015). However, the analgesic and anti-inflammatory activities of these compounds are not known although, the analgesic and anti-inflammatory activities of the stem bark and leaf of M. lucida had been reported (Mezui et al., 2017; Nwobodo et al., 2011). The aim of this study therefore is to isolate, characterize and evaluate the analgesic and anti-inflammatory activities of these iridoids. And to also determine the mechanisms of their analgesic and anti-inflammatory actions using in vivo and in silico models.