The differences in metabolites in male and female individuals of dioecious Morus alba L. (Moraceae) are usually ignored and lack study. In the present study, 58 leaves and 61 stem barks from male and female individuals were analyzed by untargeted metabolomics via headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) coupled with chemometrics, including principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA). A total of 66 and 44 metabolites were identified from leaves and stem barks, respectively. Four and eight differential metabolites among candidate metabolites in leaves and stem barks from male and female individuals were identified. Moreover, females possessed stronger antioxidant activity than males. This is the first report where untargeted metabolomics coupled with chemometrics was used to analyze the different metabolites and to discriminate the gender of leaves and stem barks of dioecious M. alba. It provided the basis for further study of M. alba and reference value for researching dioecious plants.

To comprehensively evaluate the quality of medicinal and edible Ziziphi Spinosae Semen (ZSS, the dried ripe seeds of Ziziphus jujuba var. spinosa) before and after rancidity during storage, some indicators including traditional sensory properties, physicochemical characteristics, and volatile compounds were analyzed. As a result, compared with the normal samples, the rancid samples of ZSS produced a darker color, a bitter taste, and an irritating odor, increased moisture content, electrical conductivity, fatty oil content, and acid value, and decreased water- and alcohol-soluble extract contents and pH value. Among them, the acid value had significant difference (p < 0.01) from 3.90 of normal ZSS to 18.68 mg/g of rancid ZSS. A total of 39 volatile compounds were identified in samples, including 20 in normal ZSS and 38 compounds in rancid ZSS. Nineteen common compounds were identified in normal and rancid samples. Among them, the content of 10 compounds such as δ-limonene, (R,R)-2,3-butanediol, and (R,S)-2,3-butanediol was decreased but that of nine compounds such as acetic acid, n-octanoic acid, and n-nonanoic acid was increased in rancid ZSS. Nineteen unique compounds such as β-phellandrene, α-pinene, and 3-carene were detected and only one compound, δ-cadinene, was not detected in rancid ZSS. In addition, eight short-chain organic acids, acetic, propanoic, butanoic, pentanoic, hexanoic, heptanoic, octanoic, and nonanoic acids, were new products in rancid ZSS, and it was speculated that the production of a series of organic acids might be the material basis of irritating odor after normal ZSS became rancid. This is the first report that a series of short-chain organic acids have been found in a rancid substance. In conclusion, there was a significant difference between normal and rancid ZSS. These indicators could be used as an early warning for judging the rancidity phenomenon of medicinal and edible ZSS. In addition, this is the first comprehensive evaluation about the rancidity process of a medicinal and edible substance.

Qingpi, the dried immature pericarp of Citrus reticulata Blanco, is a commonly used medicinal food with some health-promoting benefits. In general, it is essential that Qingpi be stored for a period of time, but there are no reports about the number of storage years needed to obtain the best quality of Qingpi. Our aim was to determine the best storage time of Qingpi by studying the physicochemical properties and metabolite changes in product stored from 1 to 5 years. As a result, the color of Qingpi became darker during storage. Both the levels of three flavonoids (hesperidin, nobiletin, and tangeretin) and total flavonoids (TFs) and the antioxidant activity decreased during storage and the total phenolics (TPs) content fluctuated during storage. Cluster analysis was performed on the color parameters measured using a color difference meter, revealing that the color of Qingpi differed before and after 3 years of storage. A total of 9 special differential metabolites were identified that could be used to distinguish the storage years of Qingpi. This is the first study to report the quality changes of Qingpi during storage. The optimized results of the quality evaluation indicated that Qingpi should be stored for no more than 3 years.

Herpetospermum pedunculosum (Ser.) C. B. Clarke (Family Cucurbitaceae) is a dioecious plant and has been used as a traditional Tibetan medicine for the treatment of hepatobiliary diseases. The component, content, and difference in volatile compounds in the female and male buds of H. pedunculosum were explored by using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) technology and multivariate statistical analysis. The results showed that isoamyl alcohol was the main compound in both female and male buds and its content in males was higher than that in females; 18 compounds were identified in female buds including 6 unique compounds such as (E)-4-hexenol and isoamyl acetate, and 32 compounds were identified in male buds, including 20 unique compounds such as (Z)-3-methylbutyraldehyde oxime and benzyl alcohol. (Z)-3-methylbutyraldehyde oxime and (E)-3-methylbutyraldehyde oxime were found in male buds, which only occurred in night-flowering plants. In total, 9 differential volatile compounds between female and male buds were screened out, including isoamyl alcohol, (Z)-3-methylbutanal oxime, and 1-nitropentane based on multivariate statistical analysis such as principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA). This is the first time to report the volatile components of H. pedunculosum, which not only find characteristic difference between female and male buds, but also point out the correlation between volatile compounds, floral odor, and plant physiology. This study enriches the basic theory of dioecious plants and has guiding significance for the production and development of H. pedunculosum germplasm resources.

Trichosanthes anguina L. (family Cucurbitaceae) is a monoecious and diclinous plant that can be consumed as a vegetable and has anti-inflammatory and antioxidant effects. The chemical composition and content of volatile compounds in female and male buds of T. anguina were explored by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) technology combined with multivariate statistical analysis. The results showed that the content of the volatile compounds was different between female and male buds. 2,2,6-trimethyl-6-vinyltetrahydro-2H-pyran-3-ol and 2,2,6-trimethyl-6-vinyldihydro-2H-pyran-3(4H)-one were the main volatile compounds in both female and male buds. Based on the multivariate statistical analysis of orthogonal projections to latent structures discriminant analysis (OPLS-DA) and t-test, the content of seven compounds was significantly different between female and male buds. The content of three compounds in male buds was higher than that in female, i.e., (E)-4,8-dimethyl-1,3,7-nonatriene, 1,5,9,9-tetramethyl-1,4,7-cycloundecatriene, and (E)-caryophyllene. Conversely, the content of (Z)-4-hexen-1-ol, (Z)-3-hexenyl benzoate, (Z)-3-hexenyl salicylate, and 2-hexen-1-ol in female buds was higher than that in male buds. This is the first report on the difference in the volatile compounds between female and male buds of T. anguina, which enriches the basic research on the monoecious and diclinous plant and provides a reference for the study of plant sex differentiation.

Hawthorn, the sliced and dried ripe fruits of Crataegus pinnatifida Bge. Var. Major N. E. Br. (Rosaceae), is an edible and medicinal substance with a variety of health-promoting benefits. Hawthorn needs to be stored in warehouses after harvesting to meet people's perennial demand. However, it is easily infested by insects of Plodia interpunctella and Tribolium castaneum during storage, which inevitably leads to poor quality and causes adverse effects on people's health. So far, there has been no report on insect-infested hawthorn. In this study, we analyzed the changes of metabolites in hawthorn before and after insect infestation and screened out potential biomarkers to effectively and quickly detect the occurrence of insect infestation. A combination analysis of ¹H nuclear magnetic resonance (NMR) and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) was used to identify the primary and secondary metabolites. By the comparison of hawthorn and insect-infested hawthorn samples, it was found that the differences were mainly manifested in the content of metabolites. The metabolites of 32 and 1463 were identified by ¹H NMR and UPLC-MS analysis, respectively. According to the parameters of VIP >1 and P < 0.05, 10 differential metabolites were screened from ¹H NMR analysis. Based on the parameters of VIP >1.0, P < 0.05, and (FC) > 1 or < 1, 47 differential metabolites were screened from UPLC-MS analysis. Therefore, a total of 57 differential metabolites were considered as differential biomarkers. The heat map analysis showed that the content of some differential biomarkers with significant pharmacological activities decreased after insect infestation. Through receiver operating characteristic (ROC) curve assessment, 52 differential biomarkers (6 of ¹H NMR analysis and 46 of UPLC-MS analysis) were screened to distinguish whether insect infestation occurred in hawthorn. This is the first report on the changes of metabolites between hawthorn and insect-infested hawthorn and on the screening of differential biomarkers for monitoring insects. These results contributed to evaluate quality of hawthorn and ensure food safety for consumers. It also laid a foundation for further research on the infestation mechanism and safe storage monitoring in hawthorn.