Background:
Based on the structure of RC-121 (D-Phe-c (Cys-Tyr-D-Trp-Lys-Val-Cys)-Thr-NH2, -
synthetic derivatives of somatostatin), some analogs were synthesized and tested for in vitro cytotoxic and antioxidant
activity.
Objectives:
The new analogs were modifyed at position 5 with Dap (diaminopropanoic acid), Dab (diaminobutanoic
acid) and Orn and at position 6 with the unnatural amino acids Tle (t-leucine).
Methods:
The in vitro cytotoxic effects of the substances were investigated against a panel of human tumor cell
lines HT-29 (Human Colorectal Cancer Cell Line), MDA-MB-23 (Human Breast Cancer Cell Line), Hep G-2
(Human Hepatocellular Carcinoma Cell Line) and HeLa (cervical cancer cell line). The antioxidant capacities
were tested by ORAC (Oxygen Radical Antioxidant Capacity) and HORAC (Hydroxyl Radical Averting Capacity)
methods.
Results:
All substances expressed significantly higher antioxidant capacity by comparison with galic acid and
Trolox. All substances showed considerable antioxidant capacity as well. Compound 2T (D-Phe-c(Cys-Tyr-DTrp-
Dap-Tle-Cys)-Thr-NH2)had the highest antioxidant effect. The compound 4T (D-Phe-c(Cys-Tyr-D-Trp-
Orn-Tle-Cys)-Thr-NH2) displayed antiproliferative effect on HeLa cells with IC50 30 µM. The peptide analog 3T
(D-Phe-c(Cys-Tyr-D-Trp-Lys-Tle-Cys)-Thr-NH2) exerted the most pronounced inhibition on the cell vitality up
to 53%, 56% and 65% resp. against MDA-MB-23, Hep G-2, HeLa in the higher tested concentration.
Conclusion:
The somatostatin analogs showed moderate influence on the vitality of different tumor cells and
could be used in changing their pathology.
In vitro antioxidant activity of acetylated derivatives of polysaccharide extracted from Ulva pertusa (Cholorophta)
