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The total arbutin content in the leaves of all the studied Bergenia plants (B. crassifolia, B. ciliata and B. x ornata) was determined. The highest values of the arbutin content have been established for B. crassifolia (58.9 ± 0.7 mg.g-¹ DW) and B. x ornata (51.0 ± 1.21 mg.g-¹ DW), and the lowest for B. ciliata (5.9 ± 0.6 mg.g-¹ DW). Arbutin concentration in the Bergenia leaves was the lowest in spring, in the autumn, on the contrary it increased. All the tested aqueous extracts caused a dose-dependent increase in diphenolase activity of fungal tyrosinase in a similar way as arbutin. On the other hand, all the ethanol extracts inhibited the diphenolase activity of tyrosinase.

Plant tissue cultures are a potential source of secondary metabolites. However, their production, when compared with intact plants, is usually lower. Phenylalanine, a biogenetic precursor of podophyllotoxin, was used to stimulate podophyllotoxin production in callus and suspension cultures of Juniperus virginiana L. The best phenylalanine effect on podophyllotoxin production was manifested in three-years-old callus cultures after a 21-days application of a 10 mmol/L concentration. A podophyllotoxin content of 0.15 mg/g DW was determined, which was about 400% higher in comparison with the control. The maximum content (0.48 mg/g DW) in newly derived suspension cultures (the 4' passage) was induced by 14-days application of a I mmol/L concentration; this was about 243% higher than the control. In one-year-old suspension cultures the highest podophyllotoxin content (0.56 mg/g DW) was recorded also after 14-days application of a I mmol/L concentration; this was about 211% higher than in the control cultures.

Callus cultures of Juniperus virginiana L. (varieties 'Hetzii', 'Glauca', 'Grey Owl') were derived from fresh leaves of garden-grown trees on Schenk and Hildebrandt medium supplemented with 3.0 mg/L of α-naphthaleneacetic acid, 0.2 mg/L of kinetin and 15 mg/L of ascorbic acid. The growth characteristics of one-year-old and two-years-old cultures were determined. The maximum biomass in all varieties was achieved on the 35th day of the cultivation period. The increase in fresh weights of two-years-old callus cultures, when compared with one-year-old callus cultures, was as follows: variety 'Hetzii' by 25%, variety 'Glauca' by 29% and variety 'Grey Owl' by 49%. J. virginiana suspension cultures (varieties 'Hetzii', 'Glauca', 'Grey Owl') were derived from two-years-old callus cultures on Schenk and Hildebrandt medium supplemented with 3.0 mg/L of α-naphthaleneacetic acid, 0.2 mg/L of kinetin and 15 mg/L of ascorbic acid. The maximum biomass of all varieties was found on the 21st day of the cultivation period. These results indicate that a sub-cultivation interval of 35 days for callus cultures and of 21st days for suspension cultures can be recommended. The callus and suspension cultures of J. virginiana of the variety 'Glauca' have the best survivability and thus provide the most biomass.