Search

Passiflora edulis Sims (passion fruit) seeds are often discarded as byproducts during juice processing. In fact, the seeds are of considerable commercial value in the food and cosmetics industry because of their rich polyphenols, especially piceatannol. In this study, high-speed countercurrent chromatography (HSCCC) was applied for the separation of stilbene polyphenols from passion fruit seeds. The n-hexane-ethyl acetate-methanol-water (1:2:1:2.8, v/v) was found to be the optimum two-phase solvent for the preparation of two major stilbenes, scirpusin B (8) and piceatannol (9) with purities of 90.2% and 94.8%, respectively. In addition, a continuous semipreparative HPLC was applied to further purify the HSCCC fractions containing minor stilbenes and obtain four new piceatannol derivatives (1-4) along with three known ones (5-7). The structures of these new compounds were determined using spectroscopic methods, including NMR, high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), and circular dichroism (CD). The isolated compounds were evaluated for α-glucosidase inhibitory activities in vitro. The result suggested that all of them exhibited more significant activity than acarbose, and passiflorinol B (2) had the strongest activity, with a IC50 value of 1.7 μM.

The results of the essential oil analysis of J. brandegeeana are presented in Table 1. GC and GC-MS analysis showed 32 compounds, representing 96.19% of the total oil. Alcohols are the dominant class of compounds, constitute 68.42% of the total oil, including phytol (33.12%), 1-octen-3-ol (14.45%), 3-octanol (14.30%), 9,12,15-octadecatrien-1-ol (6.10%), and trans-2-pinanol (0.45%). Aldehydes and ketones constitute 9.92% of the total oil. Ester and alkanes constitute only 6.59% and 1.10% of the total oil, respectively. The aerial parts of J. brandegeeana were collected during the flowering stage from Guilin, Guangxi, China in June 2011. A voucher specimen have been deposited in the Herbarium of the Guangxi Institute of Botany (IBK00055519). The fresh leaves of the plant (300 g) were subjected to hydrodistillation for 4 h using a Clevenger-type apparatus. The clear yellowish oil was isolated in a yield of 0.1% (w/w). The constituents of the oil were analyzed by GC and GC/MS. GC analysis of the volatile components was carried out using an Agilent 7890 instrument coupled to a flame ionization detector (FID). Compounds were separated on a HP-5 capillary column (30 m 0.25 mm, film thickness 0.25 m). The column temperature was kept at 50C for 1 min and programmed to 230C at a rate of 5C/min, and kept constant at 230C for 6 min and then programmed to 300C at a rate of 10C/min. Injector and detector temperatures were 250C, and the flow rate of helium as carrier gas was 1 mL/min. Retention indices (RI) were determined in relation to a homologous series of n-alkanes (C8–C24) under the same conditions. Relative concentrations of the components were obtained by peak area normalization. No response factors were calculated. GC/MS analysis was performed using an Agilent 5975 mass spectrometer coupled to an Agilent 7890 gas chromatograph equipped with an HP-5MS capillary column (30 m 0.25 mm, film thickness 0.25 m). The carrier gas was helium, and the chromatographic conditions were as above. All mass spectra were acquired in the electron-impact (EI) mode with an ionization voltage of 70 eV. Identification of the individual oil components was accomplished by comparison of their mass spectral data with the MS library (NIST 98 and Wiley 5) and literature values. Identification of the oil components was also possible by comparison of their linear retention indices with those from the literature [9–13] and those stored in the MS library [NIST database ChemStation data system]. For the purpose of quantitative analysis, the area percent obtained by FID was used as base.