2005; Jeffrey, 1978). The two thermo- stable chemical compounds (Krieger, 2001) are classified as triterpenoids (Chen et al., 2005; Van Wyk and Wink, 2012). A, which is solu- Preliminary ble in water (Jeffrey, 1978), is unstable and readily oxidises to cucumin (C27 H40O9) and leptodermin (C27H38O8), whereas the insoluble cucurbitacin B and Regional is stable (Jeffrey, 1978). Fruit of wild cucumber and wild are seasonal, but cannot be stored in fresh form due to the high incidents of Reports postharvest decays. Mphahlele et al. (2012) identified the causal agent as the acid-loving fungus Penicillium sim- Suitable Drying Temperature for Preserving plicissimum. Usually, fungal decay pro- motes losses of constituents of the in Fruit of Wild Cucumber and affected organs. Fungi digest food out- side its cells by secreting acids and Wild Watermelon powerful hydrolytic enzymes that de- compose complex molecules into sim- 1,3 2 pler compounds that the fungus can Kagiso Given Shadung , Phatu William Mashela , absorb and metabolize (Campbell, and Maboko Samuel Mphosi1 1990). Fungal decays have been ame- lioratedthroughdrying,whichhad been successfully used to preserve ac- africanus Cucumis myriocarpus ADDITIONAL INDEX WORDS. , , degradation, tive ingredients in most organs used medicinal system, triterpenoid, volatilization, wild cucumber, wild watermelon in various medicinal systems (Danso- SUMMARY. The thermostable cucurbitacin A and B from mature fruit of wild Boateng, 2013; Diaz-Maroto et al., cucumber (Cucumis myriocarpus) and wild watermelon (Cucumis africanus), 2002; Mudau and Ngezimana, 2014; respectively, are used in product development for various industries. Mature fruit Rocha et al., 2011). from wild cucumber and wild watermelon suffer from high incidents of postharvest The recommended drying tem- decays. Drying fruit at the recommended temperatures of 30 to 40 C for medicinal perature range for various organs in resulted in molds developing on the material, with optimum temperature to medicinal plants is 30 to 40 C prevent decays being at 52 C. The influence of 52 C and higher temperatures on (Muller€ and Heindl, 2006). How- 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 ever, when fruit pieces of the wild temperatures above the 52 C standard on concentrations of cucurbitacin A and B in cucumber and wild watermelon were fruit of wild cucumber and wild watermelon. Fruit pieces were oven-dried at 52, 60, dried within the recommended range, 70, 80, 90, and 100 C for 72 hours. Relative to 52 C, higher temperatures resulted most of the cucurbitacin materials in 25% to 92% less cucurbitacin compared with the maximum produced at 60 C. In were lost to decay, with a blue, bluish- contrast, relative to 52 C, higher temperatures reduced concentrations of cucur- green, or olive green colors, sur- bitacin B by 47% to 86%. In conclusion, the compromise temperature of 52 C for rounded by white mycelium and preserving fruit pieces in wild cucumber and wild watermelon from decay should a band of water-soaked tissues that also be viewed as the optimum temperature for preserving cucurbitacin A and B. characterize P. simplicissimum infec- tion. A preliminary optimum drying ruit of wild cucumber and wild wild watermelon contain cucurbitacin temperature to prevent growth of my- watermelon are used in medic- A(C32H46O9) and cucurbitacin B celia and, therefore, subsequent decay, Final systems, nutrition, phar- (C32H46O8), respectively (Chen et al., was established at 52 C(Mashela, maceutical, cosmetic, and pesticidal industries (Lee et al., 2010; Mashela et al., 2011; Thies et al., 2010; Van Wyk and Wink, 2012; Van Wyk et al., Units To convert U.S. to SI, To convert SI to U.S., 2002). Fruit of wild cucumber and multiply by U.S. unit SI unit multiply by

1 29.5735 fl oz mL 0.0338 Limpopo Agro-Food Technology Station, Univer- 0.3048 ft m 3.2808 sity of Limpopo, Private Bag X1106, Sovenga 0727, South Africa 2.54 inch(es) cm 0.3937 25.4 inch(es) mm 0.0394 2 Green Technologies Research Centre, University of 1 micron(s) mm1 Limpopo, Private Bag X1106, Sovenga 0727, South 1 mmho/cm dSÁm–1 1 Africa 0.1333 mm Hg kPa 7.5006 3Corresponding author. E-mail: kagiso.shadung@ul. 28.3495 oz g 0.0353 ac.za. 1 ppm mgÁmL–1 1 doi: 10.21273/HORTTECH03400-16 (F – 32) O 1.8 F C(C · 1.8) + 32

816 • December 2016 26(6) 2002). However, there was no infor- of fruit from each treatment were (Table 1). Increasing temperatures mation on the impact of this and higher extractedinclosedconicalflasks contributed 65% and 71% in TTV of temperatures on cucurbitacin A or B containing 100 mL methanol and cucurbitacin A and B concentrations, concentrations in fruit of wild cucum- dichloromethane at 1:1 (v/v) solution respectively. ber and wild watermelon. The objec- inside a rotary evaporator (Rotavapor RELATIVE IMPACT. The highest tive of this study was to determine the model R-205; Buchi Labortechnik, concentration of cucurbitacin A oc- relative effects of increasing drying Essen, Germany) set at 60 rpm at curred in fruit dried at 60 C. The temperatures above 52 C on con- 40 C for 4 h. After extraction, sub- higher temperatures reduced cucur- centrations of cucurbitacin A and B samples were concentrated by reduc- bitacin A by 25% to 92%. In contrast, in fruit of wild cucumber and wild ing the volume to 30 mL under temperatures above 52 C reduced watermelon. reduced pressure on a rotary evapora- cucurbitacin B by 28% to 86%. tor and then 1 mL aliquot centrifuged GENERATED MODELS. A quadratic Materials and methods at 2422 gn for 10 min before filter- relationship was observed between m STUDY SITE AND RAISING WILD ing through 0.22- m filter (Miller; cucurbitacin A and B concentrations 2 CUCUMBER AND WILD WATERMELON. Sigma-Aldrich, Johannesburg, South and drying temperature with an R of The study was conducted at the Africa). Concentrations of cucurbitacin 0.94 and 0.95, respectively (Fig. 1). Green Technologies Research Cen- were quantified using the isocratic ter, University of Limpopo, South elution high-performance liquid chro- Discussion Africa (lat. 2353#10$S, long. matography (Prominence model LC- Concentrations of cucurbitacin A 2944#15$E). Soil at the site com- 10 AD VP; Shimadzu, Kyoto, Japan) and B triterpenoids (Chen et al., 2005) prised Hutton sandy loam (65% sand, with detection using a diode array were inversely related to drying tem- 30% clay, 5% silt) containing 1.6% detector (CTO-20A; Shimadzu). Quan- perature. Others (Du et al., 2003; organic carbon, with electrical con- tification was performed in a wide Hwang et al., 2014) observed that ductivity of 0.148 dSÁm–1 and pH of pore reverse phase C18 (25 cm · concentrations of ginsenoside (another 6.5. The hot and dry summers usu- 4.0 mm, 5 mm) column (Sigma- triterpenoids) from ginseng roots de- ally have day maximum temperatures Aldrich, Milan, Italy) using methanol creased when dried at 40, 55, or 70 C. ranging from 28 to 38 C, with mean and deionized water at 2:3 (v/v) Similar findings were noted with annual rainfall below 500 mm. Seed- solution that served as a mobile phase the pyrethrins—the monoterpenoids lings of wild cucumber and wild wa- at a flow rate of 1.0 mLÁmin–1 in an (Morris et al., 2006). Rosmarinic acid termelon were raised in adjacent oven at 35 C, with wavelengths and sinenselin (phenolic compounds) separate fields, containing five plots monitored at 230 nm for 43 min. from misai kucing (Orthosiphon (1 · 1 m), each plot with four plants. Quantification of cucurbitacin A and staminiues), increased with increas- One experiment evaluated cucurbitacin B was accomplished by comparing the ing temperature below 40 C, but A from fruit of wild cucumber, whereas retention times and peak areas of decreased when dried at 40, 55, or the second experiment only evaluated subsamples to those of pure (about 70 C (Abdullah et al., 2011). Drying bush tea (Athrixia phylicoides)be- cucurbitacin B from wild watermelon 98%) cucurbitacin A and B standards tween 45 and 65 C reduced total (Wuhan ChemFaces Biochemical Co., fruit. Each was fertilized once phenolic content when compared Wuhan, China). Standards were dis- using3gof6.3N–9.4P–6.3Kfertilizer with freeze- and shade-drying (Mudau (Omnia, Bryanston, South Africa) and solved in methanol and prepared in and Ngezimana, 2014). plots irrigated weekly using sprinklers. serial dilutions of 0.02, 0.04, 0.06, The reduction of chemical com- –1 EXPERIMENTAL DESIGN AND 0.08, and 1.0 mgÁmL . pounds with increasing drying tem- TREATMENTS. Sixty fruit from each DATA ANALYSIS. Cucurbitacin A perature has been attributed to the plot were harvested at fruit maturity and B data were subjected to analysis accelerated degradation of the com- (Shadung et al., 2015), chopped into of variance procedure using SAS pounds (Phillips et al., 1960), which pieces, and divided equally into six software (version 9.2; SAS Institute, depends on the chemical bonds portions. Each portion per plot was Carry, NC). When treatments were within the chemical compounds randomly assigned to one of the six significant, the sums of squares were (Phillips et al., 1960). In essential forced-air drying ovens (EcoTherm; partitioned to determine the percent- oils, for example, drying temperature Labotech, Cape Town, South Africa). age contribution of sources of varia- for oregano (Origanum vulgare ssp. The drying treatment ovens were set tion to the total treatment variation hirtum) was optimized at 40 C for at 52, 60, 70, 80, 90, or 100 C and (TTV) in concentration of cucurbitacins. 72 h (Novak et al., 2011), whereas at arranged in a complete randomized Mean separation was achieved using higher temperatures most essential design, with five replications. Each Waller–Duncan multiple range test. oils were volatilized (Faridah et al., drying treatment ran for 72 h and Unless otherwise stated, only treat- 2010; Radunz€ et al., 2003). Cucurbi- afterward the samples were ground in ment means significant at the proba- tacins are thermostable, with boiling a Wiley mill to pass through a 1-mm bility level of 5% were discussed. temperatures of cucurbitacin A and B sieve. Before extraction, samples were being at 731 and 699 C, respectively, stored in hermetically sealed plastic Results at 760 mm Hg (Krieger, 2001). The bottles at room temperature. TREATMENT EFFECTS. Increasing decrease in cucurbitacin with increas- EXTRACTION AND CUCURBITACINS oven-drying temperatures had highly ing temperature agreed with observa- QUANTIFICATION. A representative significant (P £ 0.01) effects on con- tions in other chemical compounds subsample of 4 g dried crude extracts centrations of cucurbitacin A and B such as ginsenosides and pyrethrins

• December 2016 26(6) 817 PRELIMINARY AND REGIONAL REPORTS

Table 1. Responses of sum of squares (SS) for cucurbitacin A and B for the variables. At temperature from concentrations from fruit of wild cucumber and wild watermelon, respectively, 40 to 70 C, Abdullah et al. (2011) to different oven-drying temperatures (n = 30). observed that the phenolic com- Cucurbitacin A Cucurbitacin B pounds tested increased with increas- Source df SS % SS % ing temperatures, which was a reflection of the stimulation stage (Liu et al., Treatment 5 79.118 65** 141.362 71** 2003). Error 24 42.039 35 58.368 29 Total 29 121.157 100 198.729 100 **Treatment effects were significant at P £ 0.01. Conclusion The drying temperature for fruit of wild cucumber and wild water- should be retained at 52 C as a compromise against decay at lower drying temperatures. However, it would be necessary to optimize the exposure period for drying fruit of wild cucumber and wild watermelon to ensure optimum retention of cucur- bitacin A and B.

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