In vitro influence of plant extracts beyond taxonomy: a comparison ...

Abstract

Detailed information on the in vivo activity of vegetal extracts on the immune system in birds and mammals, mainly the farmed ones, is helpful in improving their resilience and welfare. Therefore there is need to investigate the exact roles of active plant components in animals, mainly their influence on the immune system, which is crucial for antimicrobial resistance. The farming system, serving principally economic aims, overlooks the physiological support of several extremely stress-sensitive, short-lived species such as chickens or rabbits. Recovering from the damage caused by adverse microclimates or nutritional deficiencies in these species can be a prolonged process often standing beyond their economic lifespan. Additionally, the compromised condition makes them susceptible to various diseases, particularly microbial or parasitic infections which can easily take hold in the weakened state. Under these circumstances, it seems very important to select and study natural enhancers of the immune response. Setting up optimal therapeutic protocols and establishing the optimal age range and administration route boost their effects. The in vitro tests, performed mainly on isolated cell- or cell-line cultures, proved the beneficial influence of certain vegetal extracts, which diminished oxidative stress and tumor growth, as well as overcame the negative effects of active oxygen species, increasing the synthesis of cytokines. The study aimed a) to establish a potential dose-effect relationship for selected plant extracts, b) considering that belonging to either of groups Aves or Mammalia changes the response to these extracts. Blood samples taken from hens and rabbits were subjected to in vitro blast transformation tests (RPMI 1640 culture medium, 48 hours of incubation in a 5% CO2 atmosphere) to estimate the effects of alcoholic extracts of Calendula officinalis, Vaccinum myrtilus, Echinacea purpurea, and Hippophae rhamnoides at 1.5% and 6.5% concentrations by a colorimetric assay (orto-toluidine test). The results in hens indicated maximal stimulation indices, in a reverse dose-dependent manner, for Vaccinum myrtillus (81.93 ± 18.74% for 1.5% concentration) and Calendula officinalis (74.70 ± 22.15% for 1.5% concentration). In rabbits, all the extracts had stimulating effects, Calendula (80.72 ± 6.82% for 6.5% concentration) and Echinacea (68.67 ± 17.04% for 6.5% concentration) being more effective than Vaccinum (65.06 ± 35.78% at 1.5% concentration). Obviously, the in vitro effects of the extracts depended on the phylogeny of the animal and the plant of origin. Thus, the birds reacted to certain extracts in an inversely dose-dependent manner, while in rabbits, the effects were directly dose-dependent. The results highlight the importance of preliminary tests in selecting an appropriate vegetal extract for immune stimulation/modulation of a given species of animals.