Biomolecules from natural sources, including microbes, have been the basis of treatment of human diseases since the ancient times. Therefore, this study aimed to investigate the potential bioactivity of several actinobacteria isolates form Al-Jouf Desert, Saudi Arabia. Twenty-one actinobac-terial isolates were tested for their antioxidant (flavonoids, phenolics, tocopherols and carotenoids) content, and biological activities, namely FRAP, DPPH, ABTS, SOS and XO inhibition, anti-hemolytic and anti-lipid peroxidation as well as their antibacterial and antiprotozoal activities. Accordingly, five isolates (i.e., Act 2, 12, 15, 19 and 21) were selected and their 90% ethanolic extracts were used. The phylogenetic analysis of the 16S rRNA sequences indicated that the most active isolates be-long to genus Streptomyces. The genus Streptomyces has been documented as a prolific producer of biologically active secondary metabolites against different cancer types. Thus, the anti-blood cancer activity and the possible molecular mechanisms by which several Streptomyces species extracts inhibited the growth of different leukemia cells, i.e., HL-60, K562 and THP-1, were investigated. In general, the five active isolates showed cytotoxic activity against the tested cell lines in a dose dependent manner. Among the potent isolates, isolate Act 12 significantly decreased the cell viability and showed maximum cytotoxic activities against both HL-60 and K562 cells, while isolate Act 15 exhibited maximum cytotoxic activity against THP-1 cells. Moreover, Act 2 and Act 12 reduced cyclooxygenase (COX-2) and lipoxygenase (LOX) activity, which is involved in the proliferation and differentiation of cancer cells and may represent a possible molecular mechanism underlying leukemia growth inhibition. The bioactive antioxidant extracts of the selected Streptomyces species inhibited leukemia cell growth by reducing the COX-2 and LOX activity. Overall, our study not only. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

BACKGROUND: Root-end filling materials are used in surgical endodontic treatment to seal the teeth periapically. Ideally, these materials should prevent bacterial leakage by tightly sealing the canal, be biocompatible with the periapical tissues, and preferably stimulate the regeneration of dentin, contributing to the success of treatment.

OBJECTIVES: The purpose of this study was to evaluate and compare the biocompatibility of the GuttaFlow® Bioseal cement in relation to MTA Angelus® and Zical® after implantation into the subcutaneous tissue of rats.

MATERIAL AND METHODS: Eighteen male albino rats were used in the study. Four polyethylene tubes were implanted in the backs of the rats (3 tubes containing the test materials and 1 empty tube as a control). Nine animals were sacrificed at each interval of 7 and 30 days, and the implants were removed with the surrounding tissue. The samples were evaluated for stromal inflammatory response, fibrous tissue formation, vascular reactivity, and the presence of multinucleated giant cells (MNGCs).

RESULTS: On day 7, the capsules in all subgroups revealed moderate to severe inflammatory reactions with the presence of inflammatory cells, multiple irregular collagen fibers, dilated blood vessels, and MNGCs. However, on day 30, tissue organization was more evident with a reduction in the inflammatory response. In this time interval, the tissue in contact with GuttaFlow Bioseal showed progressive healing with a wellformed fibrous capsule. Conversely, the tissue close to MTA Angelus revealed a fibrous capsule of limited organization with mild pericapsular fibrosis and vascular congestion. Zical showed a mild to moderate persistent inflammatory reaction and vascular reactivity.

CONCLUSIONS: The 3 cements demonstrated more severe irritation at the beginning that became milder with time. GuttaFlow Bioseal yielded better tissue organization than MTA Angelus and Zical. Thus, these findings strongly suggest that GuttaFlow Bioseal is a promising material for root-end filling.