Determination of chlorophylls and their derivatives in Gynostemma pentaphyllum Makino by liquid chromatography–mass spectrometry

The objectives of this study were to develop a high performance liquid chromatography–mass spectrometry (HPLC–MS) method for determination of chlorophylls and their derivatives in Gynostemma pentaphyllum Makino, a traditional Chinese herb possessing vital biological activities. Chlorophylls were extracted with a quaternary solvent system of hexane–acetone–ethanol–toluene (10:7:6:7, v/v/v/v), followed by separation of a total of 15 chlorophylls and their derivatives within 32 min using a gradient mobile phase of acetone, acetonitrile and methanol and a HyPURITY C18 column, with detection at 660 nm and flow rate at 1 mL/min. Identification was carried out on the basis of retention behavior, absorption spectra and mass spectra using atmospheric pressure chemical ionization (APCI) in positive ion mode for detection. Of the 15 analytes, chlorophyll a, chlorophyll b, pheophytin a and pheophytin b were quantified by using standard calibration curves, with the other 11 being quantified with an internal standard Fast Green FCF. Chlorophyll extracts in G. pentaphyllum were found to contain pheophytin a (2508.3 μg/g), pheophytin a′ (111.2 μg/g), chlorophyll a (113.8 μg/g), chlorophyll a′ (11.0 μg/g), hydroxypheophytin a (88.6 μg/g), hydroxypheophytin a′ (66.5 μg/g), pyropheophytin a (76.0 μg/g), hydroxychlorophyll a (23.8 μg/g), pheophytin b (319.6 μg/g), pheophytin b′ (13.2 μg/g), chlorophyll b (287.9 μg/g), chlorophyll b′ (11.1 μg/g), hydroxychlorophyll b (15.0 μg/g), hydroxypheophytin b (11.2 μg/g) and hydroxypheophytin b′ (8.5 μg/g).