# The Effect of Selected Herbal Extracts on Lactic Acid Bacteria Activity
## 4 Discussion
### TPC and Antioxidant Capacities of Plant Extracts  
It is reported that the metabolites present in plant extracts, including phenolic compounds, are responsible for their various biological activities, such as total phenolic content and antioxidant activity [20; 66; 67; 68; 22]. Therefore, it is worth analyzing the research proving the antioxidant activity of selected herbal extracts. Phenolic compounds are widespread in the world of plants. Based on the structure of the carbon skeleton, phenolic compounds can be divided into phenolic acids and flavonoids. [PERSON] et al. [69] and [PERSON] [66] indicated that sesquiterpenes, iridoids, flavonoids, and alkaloids were isolated from valerian (_V. officinalis_ L.) extracts. [PERSON] et al. [67] showed the lowest antioxidant activity for valerian extracts among the eight tested plant extracts (_V. officinalis_, _Melissa officinalis_, _Centaagus monogyna_, _Hypericum perfontum_, _Serratia cornotata_, and their two combinations): oxygen radical absorbing capacity--820.5 \(\pm\) 21.9 \(\upmu\)mol TE/g; hydroxyl radical averting capacity--381.6 \(\pm\) 14.0 \(\upmu\)mol GAE/g; and polyphenic content--43.36 \(\pm\) 1.3 mg/g. In our study, the valerian extract showed slightly less TPC, expressed as mg GAE/g extract, compared to the above value, despite the fact that its chemical composition included a large diversity of ingredients with antioxidant properties. Furthermore, compared to the other tested plant extracts, its antioxidant capacities were lower. The crude extract of sage (_S. officinalis_ L.) studied by [PERSON] et al. [70] contained hydroxybenzoic acids, hydroxycinamic acids, flavonoids, and diterpneoids, in addition to caffe acid, carnagic acid, luteolin, luteolin-7-O-glucoside, and rosmarinic acid. However, the composition of the plant extract may vary depending on the method used for extraction [5; 71; 72; 73]. The sage extract obtained by [PERSON] [5] also contained cyclic monoterpnees, such as 1,8-cineol, \(\alpha\)-pinene, and camphor. The crude extract and subfractions demonstrated varying degrees of antioxidant capacity. Rosmarinic acid and abietane diterpenes were thought to be responsible for the potent scavenging properties of Salvia taxa [74; 75]. Our research confirmed a good correlation between the high TPC in the sage extract and its high antioxidant capacities. Modern analytical methods based on semipreparative HPLC, high-resolution MS, nuclear magnetic resonance spectroscopy, infrared spectroscopy, and single-crystal X-ray diffraction were used to analyze the chemical composition of different sage extracts obtained from the areal parts. A substantial difference was found between the composition of sage flower CO2 extract and that of sage flower resin extract [76]. In addition to the known compounds, novel compounds were identified in sage flowers. Among these, some were preidentified in our research, namely danshensu, caffe acid, rosmarinic acid, luteolin, and apigenin. The basic active substances of chamomile (_M. chamomilla_ L.) include essential oils, flavonoids, coumarins, sesquiterpenes, polyacetylenes, spiroether, choline, mucus compounds, vitamin C, and mineral salts. Chamomile oil contains compounds that have a specific healing effect, such as antialergic chamazulene and bisabolol and its oxides. Many bioactive phenolic compounds, including herniarin and umbelliferone (coumarin), chlorogenic acid and caffe acid (phenylpropanoids), apigenin, apigenin-7-O-glucose, luteolin and luteolin-7-O-glucose (flavones), quercetin and rutin (flavonols), and naringenin (flavanone), have been found in chamomile extract [77; 78; 79]. Among flavonoids, apigenin is the most promising due to its multiple therapeutic functions. It exists in the form of various glycosides or in very small quantities as free apigenin. The method of extraction not only determines the chemical composition of chamomile extract but also its antioxidant activity [72]. Flavonoids represent the major fraction of water-soluble components in chamomile [71].