Fructus Amomi (FA) is usually regarded as the dried ripe fruit of Amomum villosum Lour. (FAL) or Amomum villosum Lour. var. xanthioides T. L. Wu et Senjen (FALX.). However, FAL, which always has a much higher price because of its better quality, is often confused with FALX. in the market. As volatile oil is the main constituent of FA, a strategy combining gas chromatography–mass spectrometry (GC-MS) and chemometric approaches was applied to compare the chemical composition of FAL and FALX. The results showed that the oil yield of FAL was significantly higher than that of FALX. Total ion chromatography (TIC) showed that cis-nerolidol existed only in FALX. Bornyl acetate and camphor can be considered the most important volatile components in FAL and FALX., respectively. Moreover, hierarchical cluster analysis (HCA) and principal component analysis (PCA) successfully distinguished the chemical constituents of the volatile oils in FAL and FALX. Additionally, bornyl acetate, α-cadinol, linalool, β-myrcene, camphor, d-limonene, terpinolene and borneol were selected as the potential markers for discriminating FAL and FALX. by partial least squares discrimination analysis (PLS-DA). In conclusion, this present study has developed a scientific approach to separate FAL and FALX. based on volatile oils, by GC-MS combined with chemometric techniques.

Here, we have found for the first time that the catalytic activity of “naked” DNAzyme, a single-stranded G-quadruplex DNAzyme (S.DNAzyme), can be modulated by aflatoxin B1 (AFB1) and zearalenone (ZEN). In fact, S.DNAzyme can mimic the activity of horseradish peroxidase to perform oxidation of 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) to colored ABTS˙⁺ (dark green). This catalytic activity can be inhibited upon addition of AFB1, leading to color fade of the solution. But with ZEN, the solution color will change to a yellowish-brown or yellow color. Thus, we have exploited this finding to achieve label-free, naked-eye detection of AFB1 or ZEN, and have explored the possible detection mechanisms. This approach is able to detect AFB1 and ZEN concentrations as low as 0.18 μM and 0.29 μM, respectively. Even in real samples, the limit of detection values of these two analytes are lower than 3 μM. Notably, S.DNAzyme cross-reacted with three other tested aflatoxins, including aflatoxin B2, aflatoxin G1 and aflatoxin M1, revealing the potential for a broadly applicable method to identify the family of aflatoxins. The AFB1- or ZEN-triggered new catalytic reaction between “naked” DNAzyme and ABTS may offer new opportunities for on-site visual detection of mycotoxins.