Antioxidant and biological activity of chamomile extracts obtained by different techniques: perspective of using superheated water for isolation of biologically active compounds

In this work, extracts of chamomile (Matricaria chamomilla L.) ligulate flowers obtained by Soxhlet, microwave-assisted, ultrasound-assisted and subcritical water extraction were compared in respect to their bioactivity, more specifically antioxidant, antimicrobial and cytotoxic activity. In all obtained extracts, the content of total phenols and flavonoids was determined, indicating significant total extraction yields (49.70%) and total phenol content (151.45 mg ECA/ml) in water extracts obtained under moderate subcritical conditions. By applying DPPH and Reducing Power Test subcritical water extraction showed superior free-radical scavenging ability in comparison to other investigated extraction techniques. Microbial properties of extracts were examined using eight selected indicator strains and for all extracts minimum inhibitory concentrations were in the range between 19.53 and 312.50 μg/ml. Subcritical water extracts showed the highest activity against Escherichia coli (MIC = 39.10 μg/ml) and Aspergillus niger (MIC = 39.10 μg/ml). Cytotoxic effects of extracts were examined on human rhabdomyosarcoma cells (RD), cell line derived from human cervix carcinoma Hep2c (HeLa) and cell line derived from murine fibroblast (L2OB). On all three tested cell lines, subcritical water extracts demonstrated much better antitumor properties in comparison to extracts obtained by other techniques, with IC50 values for Hep2c, RD and L2OB cells 30.54, 20.54 and 19.65 μg/ml, respectively.