Sustainable experimental cultivation of the Greek endemic Helichrysum amorginum Boiss. and Orph.: Assessment of the total phenolic content at different flower harvest stages

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Helichrysum amorginum Boiss. and Orph. constitutes a range-restricted, endemic species of Greece with known pharmaceutical potency. The current work presents the results of a targeted evaluation of the total phenolic content (TPC) of methanolic extracts of H. amorginum flower heads under cultivation conditions at three consecutive harvest stages in two separate cultivation locations across a period of two years (2018 and 2019). The harvested inflorescence tissue was assessed for TPC via the Folin–Ciocalteu method in three and four-year old H. amorginum individuals. Older plants, during the second evaluation year, generally showed higher flower TPC content throughout. The pooled analysis of the results indicated significant differences in TPC among samples of extracts prepared with plant material from different harvest stages with the early flowering stage (A) presenting higher TPC in both experimental cultivation locations (142.6-156 mg GAE g-1 extract on average among the two cultivation locations) followed by the full bloom stage (B) (139-145.7 mg GAE g-1 extract on average) and the late bloom or early post-anthesis stage (C) which showed the lowest TPC in all cases (130.3-131 mg GAE g-1 extract on average). The current results provide for the first-time basic information on the optimum inflorescence harvest stage during the prolonged flowering period of cultivated H. amorginum in terms of TPC. The proposed work can be incorporated into the establishment of a sustainable cultivation protocol for achieving polyphenol-rich extracts and ultimately contributes to the utilization of H. amorginum in the pharmaceutical/cosmetic sectors.