BACKGROUND The fruits of Aronia melanocarpa Elliot (Rosaceae), (black chokeberry), and Sambucus nigra L. (Caprifoliaceae), elderberries are rich in anthocyanins. Many studies have reported that anthocyanins are beneficial in diabetes due to their capacity to stimulate insulin secretion and reduce oxidative stress. OBJECTIVE The purpose of this study is to prove the biologically active properties of polyphenols extracted from S. nigra and A. melanocarpa fruit. The study also details the influence of plant polyphenols on immune system imbalances within diabetes mellitus. METHODS Polyphenolic extract was administered to Wistar rats 0.040 g/kg body every 2 d for 16 weeks. The absorbencies of all the solutions were determined using a V-550 Able Jasco UV-VIS spectrophotometer. The immunomodulatory capacity of vegetal extracts was assessed by studying cytokines TNF-α and IFN-γ through the ELISA method and fibrinogen values. CONCLUSIONS At 48 h, the anti-inflammatory effects of S. nigra and A. melanocarpa substances have been revealed by an increase of the TNF-α and IFN-γ levels in the diabetic group protected by these extracts. Seventy-two hours post-administration of both substances in the diabetic groups, the TNF-α level returns to the values read 24 h after substance administration. The vegetal extracts limit the production of fibrinogen in the diabetic rats under polyphenolic protection, the values being highly significant compared with the diabetic group. CONCLUSIONS Natural polyphenols extracted from S. nigra and A. melanocarpa modulate specific and non-specific immune defenses in insulin-deficiency diabetes and reduce the inflammatory status and self-sustained pancreatic insulitis.