Withaphysalin-type withanolides from Physalis minima
Graphical abstract
Introduction
Physalis minima Linn. (Solanaceae) is an annual herb wildly growing in the southeast of China. The whole plant was traditionally used as antibacterial and anti-inflammatory medicine in China (Chinese Herbal Medicine, 1999). Phytochemical studies revealed that it contains various withanolides, especially physalin-type and withaphysalin-type withanolides as its main constituents (Ma et al., 2007, Sahai and Kirson, 1984, Kirson et al., 1976, Glotter et al., 1975, Oshima et al., 1987). The withaphysalins are a group of naturally occurring withanolides, in which C-18 and C-20 are appropriately oxidized and cyclized in order to form a hemiacetal or a lactone. This type of compounds has only been found in genera Dunalia, Iochroma, Physalis, Vassobia and Acnistus so far (Chen et al., 2011, Guan et al., 2014). Continuing investigation of this plant led to the isolation of nine new withaphysalin-type withanolides (see Fig. 1). Herein, the isolation, identification and bioactivities of these compounds are presented.
Section snippets
Results and discussion
Compound 1 was isolated as a white amorphous powder. The molecular formula of 1 was determined as C30H42O8 based on the [M + Na+] peak at 553.2773 in HRESIMS (calcd. 553.2772). The IR spectrum showed absorption for OH groups (3419 cm−1) and α,β-unsaturated carbonyl group (1687 cm−1). The 13C NMR spectrum, in combination with HSQC, exhibited the presence of 30-carbons, including 6-methyls, 6-methylenes, 10-methines and 8-quaternary carbons. The 1H NMR spectrum showed typical withanolide signals (δH
General experimental procedures
The analysis HPLC was carried out using an Agilent1260 instrument equipped with multiple wavelength diode array detector (DAD). Preparative HPLC was performed on Shimadzu apparatus with a Shim-pack RP-C18 column (20 × 200 mm, i.d.) at a flow rate of 10 mL/min. Optical rotations were obtained on a JASCO P-1020 polarimeter (Na filter, λ = 589 nm). Circular dichroism (CD) spectra were carried out on a JASCO 810 spectropolarimeter. UV spectra were obtained on a Shimadzu UV-2501 PC spectrophotometer. IR
Acknowledgments
This work was supported by the Fundamental Research Funds for the Central Universities (JKZD2013008), New Century Excellent Talents in University (NCET-12-0977) and the Project Founded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).
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