Plants are a natural source of phytochemicals, many of which have favorable bioactive properties for human health and are therefore used in ethnomedicine for preventing and treating a variety of diseases [1]. Epilobium angustifolium (fireweed) is a popular medical plant that is known and used worldwide. Due to its abundance of secondary metabolites such as polyphenols, tannins, and terpenes, fireweed has antioxidant, anti-inflammatory, and anti-aging properties [2]. Cannabis sativa (industrial hemp) is mainly cultivated as a source of industrial fiber or seed oil. In addition to cannabinoids, the chemical composition of industrial hemp includes many other active compound groups, mostly tannins and polyphenols [3]. The biological activity of the herb is dependent on its geographical origin and the sample preparation procedure [4].
The aim of the present study was to quantitatively determine the total phenolic and flavonoid contents and characterize the volatile compositions of three different plants growing in Estonia: fireweed and the industrial hemp varieties Finola and Estica. The volatile compounds were extracted from dried samples using headspace SPME (solid-phase microextraction) and analyzed through use of GC-MS. Polyphenols and flavonoids were investigated in plant ethanol extracts through use of colorimetric tests. As a result of SPME-GC-MS, over 15 volatiles were quantified (≥1%) in each sample. The volatile compound compositions were similar in all of the samples, and the volatiles with the highest contents detected were β-caryophyllene and humulene. Colorimetric tests showed high concentrations of polyphenols (up to 157.6 ± 8.1 mg GAE/g) and flavonoids (up to 11.7 ± 0.9 mg QE/g), whereas the fireweed extracts indicated higher levels. The obtained results show that the investigated plants, fireweed, Finola, and Estica, are valuable sources of phenolic and volatile phytochemicals.
Author Contributions
Conceptualization, P.J. and M.V.; methodology, software, validation, formal analysis, and investigation, P.J. and K.D.; resources, M.V.; data curation, writing—original draft preparation, writing—review and editing, and visualization, P.J. and K.D.; supervision, P.J.; project administration and funding acquisition, M.V. All authors have read and agreed to the published version of the manuscript.
Funding
This research was supported by the Estonian Center of Analytical Chemistry (ECAC) funded by the Estonian Research Council (TT4) and the R&D project SS22004 “Evaluation of antioxidant and antibacterial activity of plant extracts” funded by Tallinn University of Technology.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to the still on-going research.
Acknowledgments
Tammejuure Organic Farm and Kanepi Municipality Government are acknowledged for kindly providing the samples.
Conflicts of Interest
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analysis, or interpretation of the data; in the writing of the manuscript; or in the decision to publish the results.
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