摘要：Bitter melon, Momordica charantia L, is a popular traditional
medicinal fruit in tropical and subtropical countries. It has been linked with
therapeutic effects, some of which are likely due to its flavonoids. To
determine its total flavonoid content (TFC) and to prepare extracts for use as
nutritional supplements or ingredients for nutraceutical functional foods,
various solvents have been used, including water, which is the preferred
solvent because it is inexpensive, safe and environmentally friendly. The study
aimed to extract bitter melon, using five solvents (ethanol, methanol,
n-butanol, acetone and water) before and after the optimal conditions for water
were determined in terms of extraction temperature, time, ratio of water to
bitter melon (mL/g) and number of times the same material was extracted. The
TFC of six varieties of bitter melon was also determined. Acetone was the best
of the five solvents for extracting flavonoids from the Moonlight variety (23.2
mg Rutin Equivalents (RE)/g). Even after increasing the extraction by 88% (1.24
vs 0.66 mg RE/g) using optimised conditions for the aqueous extraction (two
extractions at 40℃ for 15 min at a ratio of 100:1 mL/g of bitter melon
powder), the flavonoids extracted from the Moonlight variety using water was
very little (5.4%) compared to acetone. Furthermore, using acetone, it was
shown that the Moonlight variety (23.2 mg RE/g) bought at a local market had
higher levels of flavonoids than the greenhouse-grown Jade (15.3 mg RE/g), Niddhi
(16.9 mg RE/g), Indra (15.0 mg RE/ g), Hanuman
(3.9 mg RE/g) and White (6.9 mg RE/g) varieties. Therefore, acetone was the
best solvent for extracting flavonoids from bitter melon and the aqueous
extraction could only be improved to extract 5.4% of the flavonoids extracted
with acetone from the Moonlight variety, which had the highest TFC of the six
varieties of bitter melon.
