Hairy Roots Cultures from the Slow-Growing and Protected Panax ginseng, Leontopodium alpinum and Gynostemma pentaphyllum as an Alternative Source of Antimicrobials

Background/Objectives: Although the potential of hairy roots in secondary metabolite including antimicrobal production has been demonstrated in many laboratories, the scale-up to industrial production might lead to undesired phenomena affecting the final products. Methods: Here, the hairy root cultures of a pilot plant was investigated for antimicrobial properties. Methanolic extract of Panax ginseng Mey., Leontopodium alpinum Cass., and Gynostemma pentaphyllum Thunb. that are slow-growing, hard-to-cultivate and endangered species, were tested for antimicrobial activity using isothermal microcalorimetry and the Kirby–Bauer assay. Results: Antimicrobial effects were detected for P. ginseng and L. alpinum extract with a minimum inhibitory concentration (MIC) at 3.6 mg·mL−1 and 15 mg·mL−1 respectively. G. pentaphyllum showed only minimal inhibition at high concentration and appeared to act as a prebiotic at sub-inhibitory concentrations instead. The Kirby–Bauer assays supported these results. Conclusions: Industrial callus culture and hairy root production are a valuable alternative to the use of field-grown plants for the production of antimicrobials and other metabolites. Effects similar to those of their field-harvested counterpart described in many pharmacopeias were observed. Finally, isothermal microcalorimetry provides a valuable tool as it can rapidly, quantitatively and accurately monitor antimicrobial efficacy even in dark or cloudy samples.