AbstractBACKGROUNDBitter melon (Momordica charantia L.) is a medicinal fruit reported to have antidiabetic properties. To grow this tropical fruit year‐round in temperate climates, greenhouse production is necessary, sometimes without insect pollinators. Suitable high‐yielding varieties with good bioactivity need to be identified. This experiment evaluated the yield of six varieties of bitter melon under greenhouse conditions and their bioactivity in terms of total phenolic and saponin compounds and total antioxidant activity determined using four assays.RESULTSThe larger varieties (Big Top Medium, Hanuman, Jade and White) were more productive than the small varieties (Indra and Niddhi) in terms of total fruit weight and yield per flower pollinated. The bioactivity (total phenolic and saponin compounds and antioxidant activity) of the two small varieties and Big Top Medium was significantly higher than that of the other three large varieties. Two antioxidant assays, 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and ferric‐reducing antioxidant power (FRAP), were shown to provide the strongest correlations with phenolic and saponin compounds of bitter melon.CONCLUSIONPreliminary research has identified Big Top Medium as the most suitable variety for greenhouse production. The rich source of phenolic and saponin compounds and their associated antioxidant activity highlight bitter melon as a valuable food. © 2013 Society of Chemical Industry