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This study focused on bio-guided isolation based on antioxidant activities from Dicranopteris linearis spores and Averrhoa bilimbi branches. The total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activities of the extracts were determined. For D. linearis spores, the ethyl acetate (EA) extract exhibited the highest TPC (120.13 ± 0.04 mg GAE/g) and TFC (21.94 ± 0.30 mg QE/g), along with strong DPPH antioxidant activity (96.3 ± 0.3% inhibition, IC50 of 39.4 ± 0.3 µg/mL). For A. bilimbi branches, the n-hexane–ethyl acetate (HEA) extract showed the highest TPC (165.21 ± 0.24 mg GAE/g) and TFC (26.20 ± 0.01 mg QE/g), with significant DPPH antioxidant activity (89.6 ± 0.7% inhibition, IC50 of 39.7 ± 1.9 µg/mL). Phytochemical investigation led to the identification of ten compounds (D1–D10) from D. linearis spores and twelve compounds (A1–A12) from A. bilimbi branches. Notably, compound A1 was identified as a new natural compound. The chemical structures were elucidated through NMR spectroscopy and comparison with existing literature. The antioxidant activities of selected compounds (D3–D5, D8–D10, and A1–A11) were evaluated using DPPH and ABTS free radical scavenging assays. Among them, compound A3 exhibited the strongest antioxidant activities (IC50 of 7.1 ± 0.1 µg/mL for DPPH and 14.8 ± 0.1 for ABTS, respectively). The results of this study highlight the potential of D. linearis and A. bilimbi for use in natural product-based antioxidant applications.

Panax vietnamensis var. vietnamensis (PVV) and Panax vietnamensis var. fuscidiscus (PVF) both belong to Panax vietnamensis species and are chemically and morphologically similar, making it hard to distinguish for the consumer. Herein, 42 PVF and 12 PVV samples were collected in Quang Nam and Lai Chau Province, respectively, and subsequently characterized by ITSr-DNA sequence data to verify their origins. Next, untargeted metabolomics combined with multivariate statistical analysis was developed to differentiate PVV and PVF. The metabolic profiles of PVV and PVF were found to be distinct and classified well using Partial Least-Squares Discriminant Analysis (PLS-DA) in the training set. Among them, seven ginsenosides were of high abundance in PVV, while six were of high abundance in PVF. Next, the test set was used to validate 13 putative differential markers found in the training set, illustrating a complete match with the expression patterns of these ginsenosides in the training set. Finally, PLS-DA and linear Support Vector Machine models both indicated distinct ginsenoside profiles of PVV and PVF without misclassification in the test set. Conclusively, the developed untargeted metabolomics approach might serve as a powerful tool for the authentication of PVV and PVF at the metabolome level.

Panax vietnamensis, or Vietnamese ginseng (VG), an endemic Panax species in Vietnam, possesses a unique saponin profile and interesting biological activities. This plant is presently in danger of extinction due to over-exploitation, resulting in many preservation efforts towards the geographical acclimatization of VG. Yet, no information on the saponin content of the acclimatized VG, an important quality indicator, is available. Here, we analyzed the saponin content in the underground parts of two- to five-year-old VG plants acclimatized to Lam Dong province. Nine characteristic saponins, including notoginsenoside-R1, ginsenoside-Rg1, -Rb1, -Rd, majonoside-R1, -R2 vina-ginsenoside-R2, -R11, and pseudoginsenoside-RT4, were simultaneously determined by HPLC coupled with UV and with a charged aerosol detector (CAD). Analyzing the results illustrated that the detection of characteristic ocotillol-type saponins in VG by CAD presented a superior capacity compared with that of UV, thus implying a preferential choice of CAD for the analysis of VG. The quantitative results indicating the saponin content in the underground parts of VG showed an increasing tendency from two to five years old, with the root and the rhizome exhibiting different saponin accumulation patterns. This is the first study that reveals the preliminary success of VG acclimatization and thereby encourages the continuing efforts to develop this valuable saponin-rich plant.