**4. Conclusions**

This study demonstrated that the aqueous extracts of field-grown and in vitro leaves of blueberry 'Toro' are a better source of total phenolics and flavonoids than those of blackberry 'Caˇ ˇ canska Bestrna', with the former having ten to almost thirty times higher content of PCs as determined by the UHPLC-DAD MS/MS technique. Low TPC and TFC values for both callus cultures were obtained. A total of 20 phenolic compounds were found in all analyzed samples. Quercetin derivatives, chlorogenic acid and gallocatechin were the dominant PCs for both field-grown and in vitro blueberry leaves, whereas quercetin derivatives, syringic and chlorogenic acid were the most abundant phenolic compounds in blackberry. Significant amounts of flavonols such as quercetin-3-*O*-rhamnoside, aesculetin and the aglycones of quercetin and kaempferol were identified only in the in vitro blueberry leaf extract, whereas the phenolic compound profiles of field-grown and in vitro leaves of blackberry were very similar. On the other hand, callus cultures of both berry cultivars had a significantly different PC profile compared to the corresponding leaves.

This study, for the first time, reported the antioxidant properties of in vitro leaves and calluses of these two berry cultivars by the FRP, ABTS•<sup>+</sup> and DPPH• scavenging activities. Opposite to the results of the PC analysis, field-grown and in vitro leaves of blackberry 'Caˇ ˇ canska Bestrna' had better FRP activity, ABTS•<sup>+</sup> and DPPH• scavenging activities than

field-grown and in vitro leaves of blueberry 'Toro', except for ABTS• scavenging activity of in vitro leaves, which did not differ between cultivars. Callus cultures of both berry cultivars showed significantly lower antioxidant activities than the corresponding leaves.

In summary, the aqueous extracts of field-grown and in vitro leaves of blackberry 'Caˇ ˇ canska Bestrna' and blueberry 'Toro' can be a good source of phenolic compounds and exhibit good antioxidant properties, whereas callus cultures of both cultivars can have potential for the production of specific phenolic compounds.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/10 .3390/horticulturae7110420/s1, Table S1: Composition of Murashige and Skoog (MS) basal medium; Table S2: The list of quantified phenolic compounds, with retention times (min), SRM transitions and specified collision energies; Figure S1: Axillary shoot proliferation of blackberry 'Caˇ ˇ canska Bestrna'; Figure S2. Axillary shoot proliferation of blueberry 'Toro'.

**Author Contributions:** Conceptualization, T.K., T.V., R.C., D.D.M. and M.B.P.; methodology, D.D.M., A.Ž.K. and M.B.P.; software, D.D.M.; validation, U.M.G.; formal analysis, T.K., D.D.M., T.V., L.P., A.Ž.K., S.P.S. and U.M.G.; investigation, T.K., D.D.M., A.Ž.K. and M.B.P.; data curation, D.D.M. and M.B.P.; writing—original draft preparation, D.D.M.; writing—review and editing, M.B.P., T.V. and R.C.; supervision, T.V., L.P., R.C. and Ž.L.T.; project administration, M.B.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Ministry of Education, Science and Technological Development of the Republic of Serbia, gran<sup>t</sup> numbers: 451-03-9/2021-14/200116, 451-03-9/2021-14/200287, 451-03-9/2021-14/200215, 451-03-9/2021-14/200168 and 451-03-9/2021-14/200007.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
