Cyclodextrins as encapsulating agents for green extraction of Helichrysum italicum phenolics

Immortelle, (Helichrysum italicum (Roth) G.Don, Asteraceae) is a flowering plant widely used in natural cosmetics. In this work, cyclodextrin (CD)-based ultrasound-assisted extraction of immortelle bioactive principles was investigated. Optimal extraction condition and amounts of various CD (α-CD, hydroxypropyl-β-CD, hydroxypropyl--CD) required for efficient encapsulation of phenolic compounds were determined in three steps. In the first step, the most appropriate CD and the extraction time were selected and compared to the extraction efficiency of water/ethanol mixtures. In the second step, 2-level factorial design was employed for selection of the factors that significantly affect the extraction efficiency. The impact of the following factors was examined: ultrasonic power, herbal material/solvent ratio, temperature, lactic acid content and glycerol content. In the third step, Box Behnken design was used for the fine-tuning of the significant extraction conditions needed to achieve the maximum amount of bioactive compounds (total phenols, total flavonoid and total phenolic acid content). The extracts were analyzed using the HPLC, GC-MS and spectrophotometric methods. The results, presented in Fig 1., indicate that ethanol (75%) was the most efficient extraction solvent. Among the tested CDs, hydroxypropyl-β-CD was the most suited for the extraction of immortelle phenolics, reaching the extraction efficiency of the 50% ethanol. Kinetic measurements have shown that the optimal extraction duration was 30 minutes. The employed 2-level factorial design showed that herbal material/solvent ratio, temperature and lactic acid content significantly affected extraction efficiency. The extracts were found to be rich in phenolic compounds, most notably caffeic acid derivatives. In general, high temperature (80 C) and high drug/solvent ratio (0.89/10 w/w) positively affected the extraction efficiency, while the addition of lactic acid (1.95 %) positively affected total phenolic acid content but not total phenolic and flavonoid content. GC/MS analysis have shown that the most represented volatile metabolite was neryl acetate, followed by -curcumene. The results have shown that the CD-based ultrasound-assisted extraction of immortelle phenolics is an acceptable green alternative to organic-solvent based extraction.