Assessment of Biochemical Composition of Fruits of Hippophae rhamnoides (Elaeagnaceae juss.), Viburnum opulus (Viburnaceae raf.) and Lonicera caerulea subsp. altaica (Caprifoliaceae juss.)

<b>Background/Objectives:</b> This study explores the biochemical diversity of <i>Hippophae rhamnoides</i>, <i>Viburnum opulus</i>, and <i>Lonicera caerulea</i> subsp. <i>altaica</i> to identify genotypes rich in bioactive compounds for breeding nutritionally valuable cultivars. <b>Methods:</b> Selected forms and cultivars of each species were evaluated for key biochemical traits. Analyses included quantification of vitamins (C, B9, B12), sugars, organic acids, carotenoids, and flavonoids using HPLC and TLC. <b>Results:</b> In <i>H. rhamnoides</i>, vitamin C content ranged widely, with 'Pamyati Baytulina Sh-9-81' reaching 156.0 mg/%, while 'Shetlastinka No. 7' showed the most favorable sugar-to-vitamin C ratio. 'Krasnoplodnaya K-14-81' had the highest carotenoids (55.3 mg/100 g), and 'Dolgozhdannaya No. 5' was notable for flavonoid richness. In <i>V. opulus</i>, considerable variation was observed in vitamin content, sugars, and dry matter; 'Zhemchuzhnoe Ozhele' and 'Shtambovaya' were rich in rutin and robinin. In <i>L. caerulea</i> subsp. <i>altaica</i>, forms No. 5, 7, and 9 stood out for vitamin C, sugar, and flavonoid content. Hyperoside, isorhamnetin, and myricetin were common, while kaempferol and hypolaetin were form-specific. <b>Conclusions:</b><i>H. rhamnoides</i> demonstrated the highest variability in biochemical composition, while <i>L. caerulea</i> subsp. <i>altaica</i> showed a particularly rich flavonoid profile. These species offer valuable genetic resources for developing biofortified cultivars suited to both nutritional and adaptive breeding goals.