| Abstract [eng] |
Buds of balsam poplar (P. balsamifera L.) are valued in traditional medicine for their wide therapeutic effect. Poplar buds and their products can be used as antibacterial, antifungal, anti-inflammatory, antipyretic and accelerating wound healing preparations. Due to the abundance of valuable bioactive compounds (e.g. pinocembrin, pinostrobin, caffeic acid, ferulic acid, balsacones, etc.), various poplar bud extracts can be applied in the food supplement, cosmetics and pharmaceutical industries. For these reasons, the development and application of efficient extraction and fractionation processes for the extraction of bioactive poplar compounds is one of the most important tasks in order to rationally process this plant raw material into higher value-added components. The aim of this work – to optimize the extraction processes of balsam poplar (P. balsamifera L.) buds growing in Lithuania with high pressure non-toxic, environmentally and human-friendly solvents (EtOH and H2O) in order to process this plant raw material into higher value-added functional components. To achieve this goal, the parameters (temperature and time) of extraction under elevated pressure (EPS-EtOH) were optimized using a response-surface methodology. Extraction conditions were: 40–80 °C temperature and 15–45 minutes extraction time (3 cycles of 5–15 minutes). EPS-EtOH at 78 °C for 18 minutes was found to yield the highest total amount of extract (53,5 g/100 g) and in vitro antioxidant compounds (TPC – 79,7 mg GAE/g PB, TEACORAC – 1459,9 mg TE/g PB, TEACABTS – 530,9 mg TE/g PB) and target compounds (pinocembrin content – 27,3 mg/g PB, pinostrobin content 7,0 mg/g PB) content. Under optimal extraction conditions, the highest yield of carotenoids (107,4 µg/g) was achieved and the amount of chlorophylls giving undesirable green color to the extracts was reduced. The hydrocarbon sesquiterpenes α-muurolene (8,6 %), γ-curcumene (7,3 %), β-curcumene (4,4 %) and trans-α-bergamotene (3,6 %) were the main volatile compounds identified to give ethanol extract aroma of wood, spices, balsam and herbs. The residue of poplar buds after optimized EPS-EtOH was further extracted with subcrisis water (EPS-H2O) under optimal conditions (110 °C, 15 min) and 6,9 g/100 g PB of polar components were additionally isolated, TEACORAC reached 71,2 mg TE/g PB, TEACABTS – 38,5 mg TE/g PB. 0,2 mg/g PB of pinocembrin was detected in P. balsamifera buds residue and no pinostrobin was detected. EPS-EtOH extract was found to be effective against gram-positive Staphylococcus aureus bacteria and inhibited the growth of Candida albicans yeast, while EPS-H2O extract had antimicrobic activity only against Staphylococcus aureus gram-positive bacteria. EPS-EtOH extract of balsam poplar buds obtained under optimal extraction conditions, effectively inhibited tyrosinase activity (108,2 mg KAE/g PB). |
