Background:
For a long time, the researchers have been looking for new efficient methods to enhance
production and obtain valuable plant secondary metabolites, which would contribute to the protection of the natural
environment through the preservation of various plant species, often rare and endangered. These possibilities
offer plant in vitro cultures which can be performed under strictly-controlled conditions, regardless of the season
or climate and environmental factors. Biotechnological methods are promising strategies for obtaining the valuable
plant secondary metabolites with various classes of chemical compounds including caffeoylquinic acids
(CQAs) and their derivatives. CQAs have been found in many plant species which are components in the daily
diet and exhibit a wide spectrum of biological activities, including antioxidant, immunomodulatory, antihypertensive,
analgesic, anti-inflammatory, hepato- and neuroprotective, anti-hyperglycemic, anticancer, antiviral and
antimicrobial activities. They have also been found to offer protection against Alzheimer’s disease, and play a
role in weight reduction and lipid metabolism control, as well as modulating the activity of glucose-6-phosphatase
involved in glucose metabolism.
Methods:
This work presents the review of the recent advances in use in vitro cultures of various plant species for
the alternative system to the production of CQAs and their derivatives. Production of the secondary metabolites in
in vitro culture is usually performed with cell suspension or organ cultures, such as shoots and adventitious or
transformed roots. To achieve high production of valuable secondary metabolites in in vitro cultures, the
optimization of the culture condition is necessary with respect to both biomass accumulation and metabolite content.
The optimization of the culture conditions can be achieved by choosing the type of medium, growth regulators
or growth conditions, selection of high-productivity lines or culture period, supplementation of the culture
medium with precursors or elicitor treatments. Cultivation for large-scale in bioreactors and genetic engineering:
Agrobacterium rhizogenes transformation and expression improvement of transcriptional factor or genes involved
in the secondary metabolite production pathway are also efficient strategies for enhancement of the valuable
secondary metabolites.
Results:
Many studies have been reported to obtain highly productive plant in vitro cultures with respect to
CQAs. Among these valuable secondary metabolites, the most abundant compound accumulated in in vitro cultures
was 5-CQA (chlorogenic acid). Highly productive cultures with respect to this phenolic acid were Leonurus
sibiricus AtPAP1 transgenic roots, Lonicera macranthoides and Eucomia ulmoides cell suspension cultures which
accumulated above 20 mg g-1 DW 5-CQA. It is known that di- and triCQAs are less common in plants than
monoCQAs, but it was also possible to obtain them by biotechnological methods.
Conclusion:
The results indicate that the various in vitro cultures of different plant species can be a profitable
approach for the production of CQAs. In particular, an efficient production of these valuable compounds is possible
by Lonicera macranthoides and Eucomia ulmoides cell suspension cultures, Leonurus sibiricus transformed roots
and AtPAP1 transgenic roots, Echinacea angustifolia adventitious shoots, Rhaponticum carthamoides transformed
plants, Lavandula viridis shoots, Sausera involucrata cell suspension and Cichorium intybus transformed roots.
An N-terminal motif in NLR immune receptors is functionally conserved across distantly related plant species
