## 3 Results  
### Biotransformation of (4R)-(-)-Carvone (1)  
The main purpose of our work was to verify and determine the ability of comminuted vegetable bioreagents to reduce \(\alpha,\beta\)-unsaturated ketones. Consequently, both enantiomers of carvone were selected for biotransformation. At the beginning, (4_R_)-(-)-carvone (1) was subjected to biotransformation by means of five vegetables and three fruits. Based on the literature [15; 16; 17], we expected carved as a biotransformation product, but we observed a mixture of products in each sample. Another course of biotransformation could lead to the formation of dihydrocarvone after the reduction of the double bond in the carvone ring. Commercial (+)-dihydrocarvone is available in the form of a mixture of two isomers: (1\(R\), 4_R_)-(+)-dihydrocarvone (2) and (1\(S\), 4_R_)-(+)-dihydrocarvone (3). Hence, to assign a given signal to a particular isomer, they were separated by column chromatography. GC analysis (Figure 1) and NMR data allowed us to determine that the transformation products were (1\(R\), 4_R_)-(+)-dihydrocarvone, (1\(S\), 4_R_)-(+)-dihydrocarvone, and dihydrocarveol. Figure 1: Chromatograms. (**a**) Products obtained by biotransformation using potato: R\({}_{\rm f}\) = 7.090, (1\(R\),2\(R\),4_R_)-dihydrocarvole (4); R\({}_{\rm f}\) = 7.260, (1\(R\), 4_R_)-(+)-dihydrocarvone (2); R\({}_{\rm f}\) = 7.560, (1\(S\), 4_R_)-(+)-dihydrocarvone (3); unreacted substrate R\({}_{\rm f}\) = 8.983, (4_R_)-(–)-carvone (1). (**b**) Standards: R\({}_{\rm f}\) = 7.322, (1\(R\), 4_R_)-(+)-dihydrocarvone (2); R\({}_{\rm f}\) = 7.574 (1\(S\), 4_R_)-(+)-dihydrocarvone (3); R\({}_{\rm f}\) = 8.998, (4_R_)-(–)-carvone (1). Based on these results, it was found that (4_R_)-(-)-carvone (**1**) was primarily reduced to (1\(R\), 4_R_)-(+)-dihydrocarvone (**2**), which was slightly reduced to alcohol **4** (Scheme 1). A comparison of the post-reaction chromatograms and standards indicated that during the reduction of the double bond in (4_R_)-(-)-carvone, more (1\(R\), 4_R_)-(+)-dihydrocarvone (**2**) than (1\(S\), 4_R_)-(+)-dihydrocarvone (**3**) was formed. On the basis of the GC chromatograms, we determined the percentage composition of the reaction mixtures obtained after the biotransformation of (4_R_)-(-)-carvone (**1**). The results are recorded in Table 2.  
The acquired results indicated that the degree of substrate conversion depended on the type of bioreagent used. It can be seen that the enzymatic system of vegetables was more effective in the transformations of (4_R_)-(-)-carvone (**1**) than the fruits used in our experiments. The comminuted potato pulp proved to be the most effective biocatalyst, since an almost complete conversion of the substrate was observed at 99.7%. A relatively high degree of conversion was also noted using celeriac for transformation, which proved to be the most effective biocatalyst from the plants belonging to the _Umbelliferous_ family (carrots and parsley) used for biotransformation. Among the fruits used, the best biocatalyst was pear, with 50.7% substrate conversion. The apple enzymatic system was proven to be essentially incapable of bioreduction (**1**). It is worth noting that although potato transformed \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & \multicolumn{4}{c}{**Products (\%)**} \\ \cline{3-5}
**Biocatalyst** & **Substrate (\%)** & \multicolumn{2}{c}{**(2) + (3)**} & **de** & **(4)** \\ \hline _Dancus carola_ L. (carrot) & 82.0 & 17 + 0.0 & 100 & 0.7 \\ _Apium gravelems_ L. var. _rapacum_ (celeriac) & 27.9 & 47.4 + 1.3 & 94 & 23.4 \\ _Petroselinum sativum_ Hoffm: (parsley) & 87.1 & 8.9 + 0.4 & 92 & 3.6 \\ _Solanum tubersum_ L. (potato) & 0.3 & 82.5 + 3.6 & 92 & 13.6 \\ _Beta vulgaris_ L. (beetroot) & 74.5 & 24 + 0.8 & 94 & 0.7 \\ _Malus pumila_ L(apple) “Golden” & 91.0 & 5.3 + 0.0 & 100 & 3.7 \\ _Malus pumila_ L(apple) “Kortland” & 96.3 & 1.9 + 0.0 & 100 & 1.8 \\ _Pyrus communis_ L(pear) “Konferencja” & 49.3 & 49.2 + 0.8 & 97 & 0.7 \\ \hline \hline \end{tabular}
\end{table}