Micropropagation of Pterocarpus marsupium Roxb. through synthetic seeds and its novel antibiofilm activities against ESKAPE pathogens

Abstract

Pterocarpus marsupium, an endangered medicinal tree, desists long distance transportation of its recalcitrant propagules, eclipsing the mass vegetative propagation and hindering the pharmaceutical application. Therefore, the present study attempted to develop synthetic seeds by encapsulating the nodal segments using sodium alginate and calcium chloride solutions. A concentration of 100 mM calcium chloride and 3 % sodium alginate proved optimum for preparing uniform synthetic seeds. The highest 76.7 % conversion response of synthetic seed into 8.16 shoots with mean shoot length (4.35 cm) was obtained on Murashige and Skoog (MS) medium containing meta-topolin (5.0 µM) and α-naphthalene acetic acid (1.0 µM) after 12 weeks of culture. However, the shoots failed to induce a rooting response on the aforementioned optimized medium. Therefore, a two-step in vitro rooting procedure was developed. Synthetic seeds of this plant retained their germination potential after storage at 4 ᵒC for eight weeks. Analysis of glutathione-S-transferase (GST) activity indicated that the in vitro culture of synthetic seed on the above medium experienced the lowest physiological stress. The regenerated plantlets were successfully acclimatized to the natural environment, where they showed more than a 90 % survival rate after three months. The heartwood aqueous extract of the tree displayed novel antibiofilm activities against multi-drug resistant ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobcter spp.) pathogens. This study facilitates the multiplication, conservation, and production of novel bioactive compounds.