Volatiles in Potentilla discolor by HS-SPME-GC-MS

Abstract

Potentilla discolor Bunge (Rosaceae) is a perennial herb widely distributed in China. The full herb, as a traditional Chinese medicine, clears heat and toxicity, treats hemostasis, and has detumescent effects in diseases such as hematemesis, hemafecia, metrorrhagia, dysenteria, and malaria [1]. Phytochemical studies indicate that terpenes, steroids, flavonoids, and polyphenols are the main compounds of P. discolor. Pharmacologic investigations indicate that gallic acid and quercetin isolated from P. discolor have favorable effects on bacteriostasis. Additionally, flavonoids are the main hypoglycemic constituents in P. discolor [2–8]. No studies have explored the volatiles of P. discolor. To identify the volatile compounds in P. discolor, we studied the essential oil of P. discolor using HS-SPME, which was subsequently analyzed by GC-MS. The air-dried full plant of P. discolor was collected in Henan Baotianman Mountain, China, in July 2011. Plants were identified by Prof. Changqin Li (Institute of Chinese Materia Medica, Henan University). Voucher specimens were deposited in the Institute of Chinese Materia Medica, Henan University (No. 20110712). Volatile organic compounds were extracted by a manual SPME holder together with 5 mL vials and PDMS-DVB fibers purchased from Supelco Inc. (Bellefonte, USA). P. discolor powder at 0.7 g was placed in vials (5 mL). Then, the SPME fiber was exposed to the upper space of the sealed vial for 30 min at 50 C to adsorb the analytes. Next, the fiber was withdrawn and inserted directly into the GC-MS inlet for desorption of the volatiles for 1 min. Volatile constituents were analyzed by HS-SPME-GC-MS analysis carried out with an Agilent 6890 N gas chromatograph equipped with an DB-5 MS capillary column (5% phenylmethylsiloxane, 30 m 0.25 mm, film thickness 0.10 m, Agilent Technologies, USA) and coupled with a 5975 B mass selective detector from the same company. The front inlet was kept at 250 C in splitless mode. The temperature program was: initial column temperature 50 C, held for 2 min and then programmed to 120 C at a rate of 4 C/min and held for 2 min. Finally, the temperature was increased to 230 C at a rate of 6 C/min and held for 10 min. As a carrier gas, helium was used at 1.0 mL·min–1. The MS detector was used in EI mode with an ionization voltage of 1553 eV. The ion source temperature was set at 230 C. The transfer line was set at 150 C. The spectra were collected at 3 scans/s over the mass range (m/z) 30–400. Retention indices were calculated using the retention times of n-alkanes injected under the same chromatographic conditions. The volatile constituents (Table 1) were identified by comparison of their linear retention indices (relative to C8–C26 alkanes on the DB-5 MS column) and their mass spectra with those of authentic standards, as well as those from RTLPEST 3.L and NIST 05.L. The percentage composition of the volatiles was computed from the GC peak areas normalized without any corrections [9–11]. The volatiles in P. discolor were presented in Table 1. Twenty-two compounds were identified, which comprised 85.97% of the volatile fraction. Table 1 showed that the main volatiles of P. discolor were terpenoids, such as caryophyllene (20.04%), D-germacrene (3.76%), 2-carene (3.45%), limonene (3.45%), -bourbonene (3.25%), and -farnesene (2.93%). Other contents were nonanal (7.39%) and 1-octen-3-ol (6.32%). Carene and farnesene have a strong aroma, and their fragrances are widely used in essences and perfumes. Limonene has antibechic, expectorant, and bacteriostatic properties [12].