Chemical constituents from Piper betle L. Var Nigra (Piperaceae)

Two fatty acid derivatives, 2-octenoic acid and 2-hexenoic acid were isolated from the extract of n hexane of the Piper betle L. Var. Nigra (Piperaceae). The chemical structures were identified on the basis of spectroscopic evidence and compared to previously reported spectra. These isolated compounds appear for the first time in the plant.


Introduction
Piper betle L., belonging to Piperaceae family, known as a traditional herbal medicinal plant and used for several health benefits in Asian countries. Currently, demand for its products such as herbal drugs, medicines, and natural herbal formulations has increased. The beneficial effects of betel leaves and its products have traditionally exploited for the treatment of several diseases like bad breath, cuts, injuries, inflammations, cold cough, indigestion, etc. Betel leaf has several characteristics such as nutritional, organoleptic, therapeutic, prophylactic, functional, antimicrobial, antioxidant and other desirable qualities which can provide a challenging opportunity to the food scientists and technologists to develop novel food products with enhanced food safety, extended shelf life. The leaf extract and EO having the above-discussed properties can also be explored for manufacturing a large number of cosmetics, medicines, pharmaceuticals, food product development in the food sector [1].
Piper betle L. var. nigra or black betle (in Indonesia known as Sirih Hitam) is a tropical plant closely related to the common piper and belongs to the Piperaceae family and the genus of piper. This genus consists of five subgenera and approximately 1400 species spread throughout tropical and subtropical regions and widely cultivated in Indonesia, India, Sri Lanka, Malaysia, Thailand, Taiwan, and other Southeast Asian countries and has a long history of over 2000 years.
Till now, a broad range of bioactive compounds including polyphenols, terpenes, etc., has been identified from the extracts and essential oil (EO) of betel leaves. The structural and functional characterization of the extract and EO bio-actives has been derived by various advanced standard methods. Most of the healthrelated benefits of betel leaves have been associated with their bioactive phenolic compounds. The extract of this highly perishable product can be used in organic synthesis, food, and beverage industry, pharmaceuticals, etc., to the environmental issues. The present review provides information on extraction techniques, identification of bioactive compounds, and their biological activities. That apart, information on processing, preservation, and health benefits along with their mechanisms has also been added [1].
In a previous study of Piper betle L. Var. nigra Two amide derivatives, piperenamide A-B have also been reported to have activity against two oral pathogenic bacteria and opportunistic pathogenic [2].
During the efforts to discover more structurally distinct natural products from this species, we encountered a new compound (Fig  1) isolated from Piper betle var. nigra leaves. Their chemical structures were elucidated by detailed spectroscopic data analysis. Herein, we present the isolation and structural elucidation of these compounds.

General
UV spectra was measured using a TECAN Infinite M200 pro, with MeOH. The IR spectra and mass spectra were recorded on a SHIMADZU IR Prestige-21 in KBr and Waters Xevo QTOF MS respectively. Using a JEOL ECZ-500, the NMR data was recorded at 500 MHz for 1 H and 125 MHz for 13 C, using TMS as internal standard. Column chromatography was conducted on the silica gel 60 (<70, 70-230 and 230-400 mesh, Merck), after which TLC analysis was carried out on 60 GF254 (Merck, 0.25 mm) using various solvent systems, in order to detect spots by irradiating under ultraviolet-visible light (257 and 364 nm) and heating of silica gel plates, sprayed with H2SO4 in N-hexane (10%).

Plant Material.
The leaf of P. betle L. var Nigra were collected from Furthermore, the plant was identified by Mr. Ismail, a staff of the Bogoriense Herbarium, Bogor, Indonesia. Finally, a voucher specimen (No. Bo-104) was deposited at the Herbarium.

Results and Discussion
The n-hexane extract from the leaf of P. betle L. var Nigra was fractionated by column chromatography on silica gel, using a gradient of n-hexane, EtOAc and MeOH (10% stepwise). The fractions were repeatedly subjected to normal phase column chromatography, to accommodate compounds 1-2.