Exploring the Potential of Low-Temperature Vacuum Drying to Improve the Bioactive Compound Content and...

For the first time, the effect of low-temperature vacuum drying (LTVD) on wild murta (Ugni molinae Turcz) was evaluated, in comparison with freeze-drying (FD) and vacuum drying (VD), to assess their capacity to preserve bioactive compounds and associated bioactivities. Murta was dried using LTVD at 20, 30, and 40 °C under a constant vacuum of 10 mbar, where FD and VD at 60 °C (VD 60) were included as comparative methods. The content of fatty acids and tocols, along with the retention of bioactive compounds and their antioxidant, anti-inflammatory, cytotoxic, and α-glucosidase inhibitory activities, were systematically analyzed. LTVD- and VD-dried murta exhibited higher polyunsaturated-to-saturated fatty acid ratios (>9.0) and markedly greater tocol contents, whereas FD maintained a more balanced ratio (<5.0) but with lower tocol levels. While FD was most effective in preserving catechin, higher levels of other phenolic compounds were observed in samples dried by LTVD at 20 and 40 °C, as well as VD 60, possibly due to the release of bound forms during processing. The drying method significantly influenced murta bioactivity. LTVD 30 preserved the highest antioxidant capacity, while topical anti-inflammatory effects on skin lesions varied by pathway, with LTVD 40 being the most effective in the TPA model and FD in the AA model. These effects were evaluated only using a topical inflammation model in BALB/c mice of both sexes; dietary effects were not assessed in this study. Regarding other bioactivities, VD 60 extracts excelled in both cytotoxic and α-glucosidase inhibitory effects, whereas FD extracts were the most effective against AGS cells and LTVD 20 against α-glucosidase. In conclusion, LTVD emerges as a promising alternative to FD and VD, showing potential to preserve bioactive compounds and key bioactivities of wild murta, although further studies are needed to elucidate the underlying mechanisms.