Anthocyanin and polyphenolic compounds present in fruits of mulberry (Morus alba L.) were determined and the influence of temperature and UV irradiation on stability of the anthocyanin-copigment complex were investigated. The copigmentation substance selected in non-anthocyanin fraction from mulberry for the study included: phenolic acid (hydroxybenzoic acid) and flavonoid (quercetin-3-O-$eta$-D-glucopyranoside). The copigmentation effect increased with the copigment content. UV irradiation had a stronger degradation effect on the copigmentation complex than heating at $80^{circ}C$. The non-anthocyanin fraction of mulberry and isolated flavonoid (quercetin-3-O-$eta$-D-glucopyranoside) from mulberry fruit predominated over other copigment substances.