Phytomedicinal Relevance of South African Cucurbitaceae Species and Their Safety Assessment: A Review

Ethnopharmacological relevance: South Africa has a very rich flora. Many of these species such as those in the Cucurbitaceae family are exploited as medicines for the treatment of various infections.

Aim of the review: The aim of the review was to synthesize the existing but scattered literature of some plant species in the Cucurbitaceae family used as sources of medicines in South Africa.

Materials and methods: A literature survey was carried out on the ethnopharmacology, phytochemistry, pharmacological relevance and safety assessment of the South African Cucurbitaceae used as medicines.

Results: A total of 11 plants namely; Coccinia rehmannii Cogn., Cucumis africanus L.f., Cucumis anguria L. var. longaculeatus J.H.Kirkbr., Cucumis myriocarpus Naudin subsp. myriocarpus, Cucumis zeyheri Sond., Cucumis metuliferus E. Mey ex Naudin, Kedrostis nana (Lam) Cogn., Lagenaria siceraria (Molina) Standl., Momordica balsamina L., Momordica charantia L., and Momordica foetida Schumach. and Thonn were identified. Various traditional medicinal uses for these plants, from common ailments to life-threatening infections were reported. Biological activities including antidiabetic, antioxidant, antimicrobial, anticancer, anti-inflammatory and hepatoprotective were reported. However, some of the plants have not been investigated for some of the biological activities related to their traditional uses. In addition, most of the studies were carried out using non-standardized extracts. Thus, only a few studies on their bioactive constituents exist. Common compounds identified within the species are hydroxycinnamic and hydroxybenzoic acids such as sinapic, gallic, vanillic and salicylic acids; flavonoids such as naringenin, quercetin, kaempferol and rutin; fatty acids such as linoleic, palmitoleic, myristic and stearic acids; the saponin glycosides, momordicin alkaloids and cucurbitacins. However, most of these compounds have not been tested for biological activities. Cucurbitacins were implicated as a major class of toxic compounds present in the plants resulting in poisoning and death.

Conclusions: Adequate knowledge of the traditional use of these plants in medicine and the parts used are very important due to the presence of toxic substances and their wide usage. Proper screening of the safety of these plants and products derived from them calls for urgent attention.

Keywords: Cucurbitaceae; Cucurbitacins; Medicine; Pharmacology; Safety assessment.