The thermostable cucurbitacin A and B from mature fruit of wild cucumber (Cucumis myriocarpus) and wild watermelon (Cucumis africanus), respectively, are used in product development for various industries. Mature fruit from wild cucumber and wild watermelon suffer from high incidents of postharvest decays. Drying fruit at the recommended temperatures of 30 to 40 °C for medicinal plants resulted in molds developing on the material, with optimum temperature to prevent decays being at 52 °C. The influence of 52 °C and higher temperatures on active ingredients in the two fruit had not been documented. The objective of this study, therefore, was to determine the relative effects of increasing drying temperatures above the 52 °C standard on concentrations of cucurbitacin A and B in fruit of wild cucumber and wild watermelon. Fruit pieces were oven-dried at 52, 60, 70, 80, 90, and 100 °C for 72 hours. Relative to 52 °C, higher temperatures resulted in 25% to 92% less cucurbitacin compared with the maximum produced at 60 °C. In contrast, relative to 52 °C, higher temperatures reduced concentrations of cucurbitacin B by 47% to 86%. In conclusion, the compromise temperature of 52 °C for preserving fruit pieces in wild cucumber and wild watermelon from decay should also be viewed as the optimum temperature for preserving cucurbitacin A and B.

Fruit of wild watermelon (Cucumis africanus) are used to manufacture nemafric-BL phytonematicide for the management of population densities of the notorious root-knot (Meloidogyne species) nematodes on various crops. However, the concentration of the active ingredient, namely, cucurbitacin B, is dependent on the developmental stage of the fruit. A field study was, therefore, conducted to establish the optimum harvest time where C. africanus fruit would have the highest concentration of cucurbitacin B in order to ensure consistent quality of the phytonematicide. Fruit were harvested weekly from 60 to 110 days after transplating, prepared for extraction and cucurbitacin B quantified using reverse phase HPLC. Concentrations of cucurbitacin B were optimised at 5.0 weeks, which translated to a 95-day harvest time after seeding.

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Jatropha zeyheri is an indigenous crop to South Africa, which contains tea brewing and medicinal properties commonly utilized by local communities in rural areas of South Africa. Domestication and commercialization of indigenous herbal teas have gained popularity in recent years however, domestication of J. zeyheri will require optimum NPK fertilizer mixture to improve the yield and quality. Therefore, the study was intended to determine whether different fertilizer application rates will optimize yield parameters of J. zeyheri tea under greenhouse conditions. At two-leaf stage, J. zeyheri seedlings were transplanted into 25 cm diameter plastic pots. Each pot was filled with heated-pasteurised sandy soil and Hygromix at 3:1 (v/v) ratio and placed in a spacing of 0.30 m × 0.30 m inter-and intra-row spacing. Six treatments constituting NPK fertilizer rates (0, 2, 4, 8, 16 and 32 g) were arranged in a randomized complete block design, with five replications. Treatments were initiated a week after transplanting, and 130 days after that, treatments had highly significant effects on chlorophyll content, leaf width and dry root mass, contributing 70, 78 and 62% in total treatment variation (TTV), respectively. In contrast, vine length, stem diameter and leaf length were significant, contributing 47, 60 and 49% in TTV, respectively. However, treatments had no significant effects on normalized difference vegetation index, number of leaves and dry shoot mass. Jatropha zeyheri plant variables exhibited positive quadratic relations with increasing fertilizer levels. Fertilizer requirements for J. zeyheri were optimized at 3.34 g fertilizer/plant, which translates to 33 kg NPK fertilizer/ha for 10 000 plants of J. zeyheri. In conclusion, J. zeyheri appears to qualify as a low-input tea crop.

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