**1. Introduction**

The plethora of intertidal and subtidal marine organisms inhabiting the *ca.* 26,000-km coastline of Africa provide a relatively untapped opportunity for the discovery of new bioactive secondary metabolites. Despite a concerted marine bio-discovery effort over the past four decades that has focused predominantly on South African marine invertebrates [1–3], only three South African marine invertebrates, *viz.* the tube worm *Cephalodiscus gilchristi*, the ascidian *Lissoclinum* sp. and the sponge *Topsentia pachastrelloides* (Figure 1), have afforded secondary metabolites whose biomedicinal potential is currently attracting international attention. Recent reports appearing in the chemical literature (June 2012–June 2015) pertaining to this cohort of secondary metabolites is overviewed. Not surprisingly, given the global problem of obtaining sufficient supplies of bioactive marine natural products from the ocean for further drug development [4], the bioactive secondary metabolites from these three South African marine invertebrates have been the subject of concerted synthetic programs geared towards producing sufficient amounts of either the natural product or potentially more bioactive analogues, for detailed biological and *in vitro* studies.

**Figure 1.** (**a**) *Cephalodiscus gilchristi* (photo: L. Lange); (**b**) *Lissoclinum* sp. (photo: S. Parker-Nance); (**c**) *Topsentia pachastrelloides* (photo: M. Davies-Coleman).
