Xanthine oxidase (XO) is an important enzyme catalyzing the hydroxylation of hypoxanthine to xanthine and xanthine to uric acid which is excreted by kidneys. Excessive production and/or inadequate excretion of uric acid results in hyperuricemia. This paper presents a detailed review of methods of isolation, determination of xanthine oxidase activity, and the effect of plant extracts and their constituents on it. Determining the content and activities of XO can be used for diagnostic purposes. Testing inhibition of XO is important for detection of potentially effective compounds or extracts that can be used to treat diseases that are caused by increased activity of XO.In vitrobioassays are used to examine test material for XO inhibition, as inhibitors of XO may be potentially useful for the treatment of gout or other XO induced diseases. Several authors reported on the XO inhibitory potential of traditionally used medicinal plants.

Among 484 Hypericum L. (Guttiferae/Hypericaceae) species, widespread in warm temperate areas throughout the world, only H. perforatum is widely used in official medicine. Hypericum perforatum has been reported as an antidepressant, antiviral, antimicrobial, anti-inflammatory, and a healing agent. The main constituents of the Hypericum species are naphthodianthrones, primarily represented by hypericin and pseudohypericin, phloroglucinol derivatives, especially hyperforin, and flavonoids, such as quercetin, quercitrin, hyperoside and rutin. Hypericin and pseudohypericin have been found to possess antiretroviral activity. Hyperforin may also have an important contribution to the antidepressant activity of Hypericum extracts. The content of the above active constituents in some Hypericum species is higher than in H. perforatum. Also, a number of studies of the biological activities of Hypericum species have shown that the most recognized species of this genus, H. perforatum, was not the most active. Comprehensive analysis of the published research on the chemical composition and biological activity, showed that H. richeri has a similar pharmacological potential as St. Jon's wort. The species, with high content of naphtodianthrones,which might be used against viruses and retroviruses, are: H. androseamum,H. annulatum, H. barbatum, H. boissieri, H. elegans, H. hirsutum, H. hyssopifolium, H. humifusum, H. montanum. H. montbretii, H. triquetrifolium, H. richeri, H. rochelii, H. rumeliacum, H. thasium, andH. patulum. Very few species (e.g. H. inodorum and H. moseranum) contained the similar amounts of hyperforine as H. perforatum. Since hyperforin was recognized as one of the most crucial components for the antidepressive activity, it seems that H. perforatum barely has an alternative for this purpose. Plant species containing considerable amounts of other acylphloroglucinol derivatives have the potential to demonstrate antibacterial and cytotoxic activity. Some of these species are: H. sampsonii, H. ascyron, H. foliosum, H. geminiflorum and H. scabrum. However, only a few studies concerning the activity of extracts and isolated compounds were done in vivo. Also, data on the safe usage of Hypericum constituents as phytotherapeutics are scarce. Since some of Hypericum species are scarcely distributed or endemic as well as some of the secondary metabolites are presented in very small amounts, bio-production, especially endophytes, could represent an abundant and reliable source of pharmacologically active metabolites of Hypericum species for exploitation in pharmaceutical industry.

The results showed that the examined species had strong antioxidant and antimicrobial properties and are in accordance with the popular use of plants belonging to the genus Allium in traditional medicine, emphasising the necessity of further detailed study of the active principles in Allium species.

The qualitative, quantitative and microbial determination of the aqueous extract of comfrey root was done in this paper. The qualitative and quantitative analyses were done by the UHPLC-DAD-HESI-MS method. Allantoin, rosmarinic acid and ellagic acid were identified as major bioactive compounds and their quantification was also done. The obtained results showed a high content of allantoin, ellagic acid and rosmarinic acid (8.91, 7.4 and 12.8%, respectively) which indicated that the comfrey root can be used as a source for the isolation of these three compounds. The results obtained by the determination of the antimicrobial activity showed that Escherichia coli ATCC 8739 and Salmonela typhimirium ATCC 6538 were most sensitive to the aqueous extract of comfrey root. The results showed that allantoin did not express the antimicrobial activity on all the investigated bacteria species, and based on this it can be concluded that allantoin is not responsible for the antimicrobial activity of the aqueous extract of comfrey root.

Characterization by GC-FID and GC/MS analyses of the Stachys officinalis (L.) Trevis. essential oil obtained by hydrodistillation of the aerial parts allowed the identification of 190 components that represented 97.9% of the total oil content. The main constituents identified were germacrene D (19.9%), β-caryophyllene (14.1%), and α-humulene (7.5%). Terpenoids were by far predominant (89.4%), with sesquiterpene hydrocarbons (69.1%) and oxygenated sesquiterpenes (14.8%) being the most abundant compounds detected in the oil. Based on the present and previously published results, multivariate statistical comparison of the chemical composition of the essential oils was performed within the species. Principal component analysis (PCA) and agglomerative hierarchical clustering (AHC) of the data on the volatile profiles of S. officinalis taxa revealed no pronounced differences among the samples originated from the Balkan Peninsula. Additionally, the oil was screened for in vitro antibacterial and antifungal activity using the broth microdilution assay. The oil's best antimicrobial activities were obtained against the mold Aspergillus niger (minimal inhibitory (MIC) and minimal fungicidal (MFC) concentrations of 2.5 and 5.0 mg/ml, resp.) and the yeast Candida albicans (MIC and MFC of 5.0 mg/ml).