Post-target Analysis for the Volatile Compounds from SaltyAlpinia oxyphyllae Fructuswith Headspace-gas Chromatography-quadrupole/time of Flight Mass Spectrometry

Abstract

Post-target analysis is a superior method for qualitative analysis. This method can make a rapid, accurate and wide-scope screening for non-target and target compounds, and it has been used widely in the metabonomics, environmental analysis and pesticide residues. With post-target method to analysis non-target compounds, retention index, accurate mass and library were applied to investigate non-target analytes and then a total of 119 compounds were identified. Within those 119 compounds, there are different kinds of compounds, such as aliphatic aldehyde, aromatic ketone, aromatic aldehyde, monoterpene and its oxide, sesquiterpenes and its oxide and so on. Eremophilene is the best peak ingredient, p-cymene, aromadendrene, nootkatone and delta-cadinene are the main ingredients. Besides, nootkatone is the main active ingredient according to previous pharmacology research. Narrow mass window extracted ion chromatograms (nw-XIC) can decrease background noise greatly and improve the signal-to-noise rate. Hence, the trace level or co-elution compounds can be identified. With the post-target analytical method for target analytes, we calculated retention time from retention index of target compounds, and then nw-XIC (mass window 0.02 Da) was carried out. Four characteristic ions of target compounds were extracted to get extracted ion chromatograms at calculated retention time. As peaks at calculated retention time had the same chromatographic behavior, we identified three target compounds: nootkatol, alpha-cyperone and perillaldehyde. Tandem mass technology has been widely used since its introduction in the 1970s, it was used in trace analysis, chemical reaction mechanistic studies and propose the fragmentation pattern of compounds. In this paper, we got first-stage mass spectra and second-stage mass spectra data in one experiment. Moreover, we could obtain accurate mass of precursor ion and product ion from second-stage mass spectra at the same time, then we inferred the MS fragmentation pattern of compounds. This method is more simple, convenient and accurate than the traditional tandem mass spectrometry. Myrtenal was identified in this post-target way. Post-target analytical method can distinguish compounds from complex matrix samples as many as possible. This method solves the problems of co-elution and high background and can be used to investigate the medicine's pharmacology and toxicology mechanism.