Phytochemical investigations on Polypodium hastatum have led to the isolation of three isomers of coumaric acid glucosides. Their structures were identified as trans-melilotoside (1), trans-coumaric acid-3-O-E-Dglucopyranoside (2), and trans-coumaric acid-4-O-E-D-glucopyranoside (3) by spectroscopic analysis. Compound 2 is a new natural product.Keywords: coumaric acid glucoside, structure elucidation, Polypodium. Polypodium hastatum Thunb. (Polypodiaceae) is a fern that belongs to the genus Polypodium and grows in most areas of China. In Chinese folk medicine, it is used as a phytomedicine for the treatment of urinary diseases. Previous phytochemical investigations on the genus revealed that there were triterpenoids [1], diterpenoids [2], steroids [2], flavonoids [2], polyphenols [2], and fatty acid derivatives [3]. But to the best of our knowledge, only a coumarin was identified by Suzuki from the leaves of P. hastatum growing in Japan [4] before our investigation. In our program to discover bioactive natural products from ferns, a phytochemical investigation of this plant was carried out, and some flavonoids have been obtained [5,6]. Herein we report the isolation and structure elucidation of coumaric acid glucosides from P. hastatum.Compound 2 was obtained as white crystals. The ferric chloride reaction showed a positive result. ESI-MS gave a molecular cation peak at m/z 349 [M + Na] + . The 1 H NMR spectrum (Table 1) showed two olefinic hydrogen signals at G 7.60 (1H, d, J = 16.2 Hz) and 6.40 (1H, d, J = 16.2 Hz), which indicated the presence a trans double bond. At the same time, the signals at G 7.55 (1H, s), 7.24 (1H, d, J = 7.8 Hz), 7.14 (1H, dd, J = 7.8, 8.3 Hz), and 6.98 (1H, d, J = 8.3 Hz) implied the presence of a meta-substituted benzene ring. In the 13 C NMR spectrum (Table 1), there was a carbonyl carbon signal at G 171.8. In the range of G 110-160, there were eight unsaturated carbon signals, which is in agreement with the 1 H NMR spectrum showing the occurrence of a double bond and a substituted benzene in the structure. Compared with the 13 C NMR spectra of compounds 1 and 3, it can be concluded that there was a glucoside moiety. The E-configuration of the anomeric carbon of the glucose was deduced from the coupling constant (J = 7.4 Hz) of the anomeric hydrogen signal at G 4.9. Based on the analysis and chemical reactions, it can be concluded that compound 2 was trans-coumaric acid-3-O-E-D-glucopyranoside. HMBC and HSQC further confirmed the proposed structure and assigned the 1 H and 13 C NMR data.The trans-coumaric acid-3-O-D-D-glucopyranoside was formerly synthesized by Funayama [7] through the catalysis of glucoside synthetase, but the E anomer is reported herein for the first time, and this investigation also revealed its presence in nature for the first time. In addition, as known phytochemicals, compounds 1 and 3 were indentified through comparison of the NMR data with the literature [8,9].