Alnus firma
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https://doi.org/ 10.1016/j.phytochem.2020.112292 |
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https://doi.org/10.5281/zenodo.8305095 |
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https://treatment.plazi.org/id/4E6E87B6-FFC7-B91F-FC97-7B34FED3E4A3 |
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Felipe |
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Alnus firma |
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2.3. Identification of α -glucosidase inhibitory compounds from Alnus firma View in CoL View at ENA
A previous study reported that H 2 O or MeOH extracts of A. firma leaves exhibited inhibitory activity against α- glucosidase ( Yu et al., 2007). However, none of the compounds isolated in this study showed α- glucosidase inhibitory activity, and other metabolites from Alnus have not been reported to exhibit α- glucosidase inhibition, except three cyclic diarylheptanoids isolated from A. sieboldiana ( Chiba et al., 2013) . We hypothesized that the chemical information derived from MS/MSbased dereplication in this study could be used to reveal which compounds contribute to the α- glucosidase inhibitory activity of A. firma , and tried to associate the annotations to bioactive extracts. 15 Alnus extracts were evaluated for their α- glucosidase inhibitory activity as shown in Table 1 View Table 1 . As previously reported, the leaf extract of A. firma exhibited potent inhibitory activity showing IC 50 values of 12.29 μg/ mL. Extracts of A. firma bark, twigs, and fruits, and A. hirsuta var. sibirica fruits also showed potent activity with IC 50 ranging from 6.80 to 8.48 μg/mL. Extract of A. japonica leaves and A. hirsuta var. sibirica leaves exhibited moderate inhibitory activity with IC 50 values of 23.36 and 29.84 μg/mL, while other extracts showed very weak or no inhibitory activity against α- glucosidase.
To bridge the bioactivity and chemical information, we applied the workflow named “bioactive molecular networking”, which was developed in our previous study ( Nothias et al., 2018). In this workflow, the Pearson correlation coefficients (r) and their significances (p values) between the semi-quantitative intensities of MS/MS features and the bioactivity value are calculated. By plotting r and p values on the molecular network, it was easily visualized that MS/MS spectra showing negative r values (negative correlation with IC 50; meaning possibly inhibitory against α- glucosidase) with significance (p <0.05) are mainly clustered within the molecular families B (ellagitannins) and G (gallotannins) ( Fig. S3 View Fig , Supplementary Data). In order to narrow down the candidates from chemical classes to single compounds, we filtered the candidate list using the Bonferroni correction for multiple hypothesis testing ( Nothias et al., 2018). As a result, only one MS/MS feature (10) was left as a possible contributor to the bioactivity showing an r value of −0.8625 (IC 50 values were applied as bioactivity index, so negative r values mean higher contribution to bioactivity) and a p value of 3.52 × 10 −5. The MS/MS feature 10 was annotated as gallic acid by spectral matching, and the identification was confirmed by standard compound injection. We inspected the MS/MS feature table and confirmed that active extracts (Af-B, Af-T, Af-L, Af-F, Aj-L, Ahv-L, and AhvF; ion intensity for 10 ranging from 49,854 to 96,211) show a higher intensity of the gallic acid ion than inactive extracts (Aj-B, Aj-T, Aj-F, Ah-L, Ah-F, Ah-B, and Ahv-T; ion intensity for 10 ranging from 520 to 11,358) as shown in Fig. 5. A View Fig previous study reported gallic acid as a potent α- glucosidase inhibitor ( Wansi et al., 2007), so it could be hypothesized that gallic acid is the main contributor of α- glucosidase inhibition of these Alnus extracts . Although this result did not provoke a discovery of a previously unknown bioactive compound, it demonstrated that the digitized MS/MS-based dereplication strategy can reveal bioactive components from complex phytochemical extracts and reduce the unnecessary effort spent in re-isolation of previously known bioactive compounds.
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