Supercritical fluid extraction of Alnus glutinosa (L.) Gaertn.

Supercritical carbon dioxide extraction of Alnus glutinosa (L.) Gaertn. was performed (P = 300/450 bar, T = 40/60 °C, EtOH addition = 0/5/10%) in order to determine preferable process conditions. Phytochemical composition of extracts were analyzed by means of TLC, GC–MS, LC–MS, RP-HPLC. Total of 11 pentacyclic triterpenes and β-sitosterol were identified. The results indicated that SFE is an advantageous method over Soxhlet extraction in terms of yield and recovery of target compounds. Overall extraction curves revealed that pressure had little influence on extraction yield, while temperature and amount of co-solvent increased it. The optimum SFE condition was 300 bar/60 °C/10% EtOH, where the amount of extracts was 3.81% compared to n-hexane (2.56%). Highest amount of betulin, betulinic acid and lupeol was 3.57, 2.95 and 14.33 g/100 g extract, respectively, depending on the applied SFE condition. Ethanolic Soxhlet extraction ensures the highest yield (40.90%), but provides the extracts diluted with undesirable substances hence the concentration of triterpenes in the extract was very low.

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► Supercritical fluid extraction of Alnus glutinosa (L.) Gaertn. was performed.
► Yields and pentacyclic triterpene composition of different extracts were evaluated.
► Pressure had little influence on the yield, while temperature and amount of co-solvent increased it.
► Presence of different triterpenoids and β-sitosterol were justified.