The colorimetric assay used for saponin quantification in plant extracts is subject to interference by common solvents used to extract the saponins from plant materials. Therefore, the degree of interference of ten common solvents was investigated. It was found that the presence of acetone, methanol and n-butanol in the reaction solution caused an intense darkening of the reaction solution in the absence of saponins, which likely could lead to erroneous saponin content values. Using aescin to construct standard curves with different solvents—such as water, ethanol, and methanol— also showed significant differences in the standard curves obtained, which led to different values when they were applied to quantify the saponin content of an ethanol extract from dried and powdered Gac (Momordica cochinchinensis Spreng) seed kernels. To improve the method, a solvent evaporation step was added prior to the colorisation reaction to prevent undesired solvent interference during the reaction step. Using this modified protocol for the aescin standard curve and the Gac seed kernel extract eliminated any solvent interference. Thus, this improved protocol is recommended for the quantification of the saponin content of plant extracts irrespective of which extraction solvent is used.

Background: Gac (Momordica cochinchinensis Spreng.) seeds contain saponins that are reportedly medicinal. It was hypothesised that the extraction of saponins from powdered Gac seed kernels could be optimised using microwave-assisted extraction (MAE) with ethanol as the extraction solvent. The aim was to determine an appropriate ethanol concentration, ratio of solvent to seed powder and microwave power and time for extraction. Whether or not defatting the Gac seed powder had an impact on the extraction of saponins, was also determined. Methods: Ethanol concentrations ranged from 60–100% were used to compare total saponins content (TSC) extracted from full-fat and defatted Gac seeds. Ratios of solvent to Gac seeds ranged from 10 to 100 mL g⁻¹ and microwave conditions ranged from 1–4 cycles at power levels ranged from 360–720 W, were examined successively to evaluate their efficiency in extracting saponins from full-fat Gac seeds. Results: A four-fold higher of TSC was obtained in extracts from full-fat Gac seed powder than from defatted powder (100 vs. 26 mg aescin equivalents (AE) per gram of Gac seeds). The optimal parameters for the extraction of saponins were a ratio of 30 mL of 100% absolute ethanol per g of full-fat Gac seed powder with the microwave set at 360Wfor three irradiation cycles of 10 s power ON and 15 s power OFF per cycle. Conclusions: Gac seed saponins could be efficiently extracted using MAE. Full-fat powder of the seed kernels is recommended to be used for a better yield of saponins. The optimised MAE conditions are recommended for the extraction of enriched saponins from Gac seeds for potential application in the nutraceutical and pharmaceutical industries.

Background: Gac (Momordica cochinchinensis Spreng) seeds have long been used in traditional medicine as a remedy for numerous conditions due to a range of bioactive compounds. This study investigated the solvent extraction of compounds that could be responsible for antioxidant activity and anticancer potential. Methods: Defatted Gac seed kernel powder was extracted with different solvents: 100% water, 50% methanol:water, 70% ethanol:water, water saturated butanol, 100% methanol, and 100% ethanol. Trypsin inhibitors, saponins, phenolics, and antioxidant activity using the 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and the ferric reducing antioxidant power (FRAP) assays; and anticancer potential against two melanoma cancer cell lines (MM418C1 and D24) were analysed to determine the best extraction solvents. Results: Water was best for extracting trypsin inhibitors (581.4 ± 18.5 mg trypsin/mg) and reducing the viability of MM418C1 and D24 melanoma cells (75.5 ± 1.3 and 66.9 ± 2.2%, respectively); the anticancer potential against the MM418C1 cells was highly correlated with trypsin inhibitors (r = 0.92, p < 0.05), but there was no correlation between anticancer potential and antioxidant activity. The water saturated butanol had the highest saponins (71.8 ± 4.31 mg aescin equivalents/g), phenolic compounds (20.4 ± 0.86 mg gallic acid equivalents/g), and antioxidant activity, but these measures were not related to anticancer potential. Conclusions: Water yielded a Gac seed extract, rich in trypsin inhibitors, which had high anticancer potential against two melanoma cell lines.

Gac (Momordica cochinchinensis Spreng.) seeds contain bioactive compounds with medicinal properties. This study aimed to determine a suitable solvent and extraction technique for recovery of important compounds, namely, trypsin inhibitors, saponins, and phenolics. The antioxidant capacity and total solids of derived extracts were also measured. Water with conventional extraction method gave the highest value of trypsin inhibitor activity (118.45 ± 4.90 mg trypsin g⁻¹) while water-saturated n-butanol and methanol extracts were characterized by their highest content of saponins (40.75 ± 0.31 and 38.80 ± 2.82 mg AE g⁻¹, respectively). Aqueous extract with microwave assistance achieved the highest phenolics (3.18 ± 0.04 mg GAE g⁻¹). As a measure of antioxidant capacity, the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) assay gave highest value to the aqueous microwave extract (23.56 ± 0.82 μmol TE g⁻¹) while the ferric reducing antioxidant power (FRAP) assay gave highest values to water-saturated n-butanol and 70% ethanol extracts (5.25 ± 0.04 and 4.71 ± 0.39 μmol TE g⁻¹, respectively). The total solids value was highest using water with microwave assistance (141.5 g kg⁻¹) while ultrasound treatment did not improve any extractions. Therefore, trypsin inhibitors are suitably recovered using water while water-saturated n-butanol or methanol is for saponins, both using a conventional method. Microwave extraction is suitable for phenolics recovery. These conditions are recommended for an efficient recovery of bioactive compounds from defatted Gac seeds.

Gac seeds are high in oil, but there are few studies on its extraction and characteristics. This study aimed to characterise Gac seeds and investigate the physicochemical properties of Gac seed oil extracted with supercritical carbon dioxide (SC-CO₂) and hexane (Soxhlet). The Gac seed kernel accounted for 66.4 ± 2.7% of the seed weight, and 53.02 ± 1.27% of it was oil. The SC-CO₂ oil had a higher quality than the Soxhlet oil for important criteria, such as peroxide (0.12 ± 0.02 vs. 1.80 ± 0.01 meq O₂/kg oil), free fatty acid (1.74 ± 0.12 vs. 2.47 ± 0.09 mg KOH/g oil) and unsaponifiable matter (33.2 ± 1.5 vs. 52.6 ± 2.4 g/kg) values, respectively. It also had a better colour (light yellow vs. dark greenish brown) and a higher antioxidant capacity measured with the DPPH (52.69 ± 0.06 vs. 42.98 ± 0.02 µmol Trolox equivalent/g oil) and ABTS (2.10 ± 0.12 vs. 1.52 ± 0.06 µmol Trolox equivalent/g oil) assays. However, a higher yield (53.02 ± 1.27 vs. 34.1 ± 0.8%) was obtained for the Soxhlet oil. Unless refined, the oils would not be edible due to their high unsaponifiable matter, but the SC-CO₂ oil would need less refining. Alternatively, the high unsaponifiable matter in the oil, especially in the Soxhlet oil, may make it useful for medicinal purposes.

The seeds of the Gac fruit, Momordica cochinchinensis Spreng, are rich in trypsin inhibitors (TIs) but their optimal extraction and the effects of freeze drying are not established. This study aims to (1) compare aqueous solvents (DI water, 0.1 M NaCl, 0.02 M NaOH and ACN)/water/FA, 25:24:1) for extracting TIs from defatted Gac seed kernel powder, (2) to optimise the extraction in terms of solvent, time and material to solvent ratio and (3) to produce a TI-enriched freeze-dried powder (FD-TIP) with good characteristics. Based on the specific TI activity (TIA), the optimal extraction was 1 h using a ratio of 2.0 g of defatted powder in 30 mL of 0.05 M NaCl. The optimisation improved the TIA and specific TIA by 8% and 13%, respectively. The FD-TIP had a high specific TIA (1.57 ± 0.17 mg trypsin/mg protein), although it also contained saponins (43.6 ± 2.3 mg AE/g) and phenolics (10.5 ± 0.3 mg GAE/g). The FD-TIP was likely stable during storage due to its very low moisture content (0.43 ± 0.08%) and water activity (0.18 ± 0.07) and its ability to be easily reconstituted in water due to its high solubility index (92.4 ± 1.5%). Therefore, the optimal conditions for the extraction of TIs from defatted Gac seed kernel powder followed by freeze drying gave a high quality powder in terms of its highly specific TIA and physical properties.