A new 5H-purin-6-amine from the leaves of Sedum sarmentosum

Phytochemical constituents were isolated from Sedum sarmentosum leaves using open column chromatography and medium-pressure liquid chromatography. Their structures were identified as 2,4-pyrimidinedione (1), N-methylhydroxylamine (2), 5H-purin-6-amine (3), uridine (4), l-tyrosine (5), and l-prolyl-l-tyrosine (6) using mass spectrometry and 1H- and 13C-nuclear magnetic resonance spectroscopic analysis. Among them, compound 3 (5H-purin-6-amine) was isolated for the first time from a natural source.


Introduction
Sedum sarmentosum Bunge is a perennial herb distributed across Asia, Europe, and North America [1]. It is commonly known as Dolnamul in Korea. Fresh leaves of S. sarmentosum have been used in salads as an alternative to pepper because of their pungent taste. Moreover, traditionally, it has been used as a hepatoprotective medicinal plant in Asian countries [2]. Few studies have focused on the biological activities of S. sarmentosum [1]. S. sarmentosum shows unique angiotensin-converting enzyme inhibitory activity. Some flavonoids also show this activity [3]. Kim et al. [4] suggested that S. sarmentosum contains estrogens to promote a better life in menopausal women [4].
The objective of this study was to find new bioactive compounds from the leaves of S. sarmentosum. Therefore, our investigation was designed for the systematic isolation and identification of these valuable phytochemicals.

Plant materials
Fresh S. sarmentosum leaves were cultivated at Juksanmyeon, Anseong, Republic of Korea.

Apparatus and chemicals
Nuclear magnetic resonance (NMR) spectra were recorded with a Bruker Avance 500 NMR (Rheinstetten, Germany) spectrometer. Mass spectrometry (MS) was performed using a JEOL JMS-600 W (Tokyo, Japan) mass spectrometer. Optical rotations were measured on a Jasco P-2000 digital polarimeter (Tokyo, Japan). Medium-pressure liquid chromatographic separation was carried out on the Biotage (Uppsala, Sweden) system.
Compound 3 was obtained as a white amorphous powder. A molecular ion peak was measured at m/z 135 [M] ? in the EI-MS, which corresponds to a molecular formula of C 5 H 5 N 5 by HREI-MS (m/z 135.0546 [M] ?, calcd. for 135.0545). 1 H-NMR spectra of 3 showed a methine proton at d 3.16 and the presence of two aromatic protons at d 8.45 and 8.46. The 13 C-NMR spectrum indicated 5 carbon resonances. The 13 C-NMR spectrum showed a methine carbon at d 48.5 and two olefin quaternary and two olefin methane carbons at d 142.7, 146.1, 149.3 and 151.4. The structure of 3 was similar to that of adenine [9]. Thus, the structure of 3 was assigned as 5H-purin-6-amine via spectroscopic analysis.
Six compounds were isolated for the first time from S. sarmentosum leaves. According to previous studies, compound 3 (5H-purin-6-amine) was isolated for the first time from a natural source.