Effect of herbal extracts on peripheral nerve regeneration after microsurgery of the sciatic nerve in rats

Background Recent experimental studies using herbal extracts have shown the possibility of peripheral nerve regeneration. This study aimed to investigate the effects of herbal extracts on peripheral nerve regeneration in a rat sciatic nerve injury model. Methods A total of 53 rats were randomly assigned to a control group or one of four experimental groups. In all rats, the sciatic nerve was completely severed and microscopic epineural end-to-end neurorrhaphy was performed. Normal saline (2 mL) was topically applied to the site of nerve repair in the control group, whereas four different herbal extracts – 2 mL each of Astragalus mongholicus Bunge, Coptis japonica (Thunb.) Makino, Aconitum carmichaelii Debeaux, or Paeonia lactiflora Pall. – were topically applied to the site of nerve repair in each experimental group. Nerve conduction studies were performed at an average of 11.9 weeks after the operation, and conduction velocity and proximal and distal amplitudes were measured. Biopsies were performed at an average of 13.2 weeks after the initial neurorrhaphy. The quality of nerve anastomosis and perineural adhesion to the surrounding soft tissues was macroscopically evaluated. The neuroma size at the site of the neurorrhaphy was microscopically measured, whereas the size of the scar tissue was evaluated relative to the diameter of the repaired nerve. Results The nerve conduction study results showed the highest nerve conduction velocity in the experimental group that used the Coptis japonica (Thunb.) Makino extract and the highest proximal and distal amplitudes in the experimental group that used the Aconitum carmichaelii Debeaux extract. Macroscopic evaluations after the second operation showed that grade 2 perineural adhesion was found in 70.8% of rats. The mean neuroma size in the Coptis japonica (Thunb.) Makino, Aconitum carmichaelii Debeaux, and Paeonia lactiflora Pall. groups showed statistically significant decreases relative to the control group. The mean scar tissue formation index in the Paeonia lactiflora Pall. group showed a statistically significant decrease relative to the control group. Conclusions The peripheral nerve regeneration effect of the herbal extracts was confirmed through decreased neuroma and scar tissue formation.

α-d-Glucopyranosyl-(1→2)-[6-O-(l-tryptophanyl)-β-d-fructofuranoside]

The Mycobacterium sp. BRS2A-AR2 is an endophyte of the mangrove plant Rhizophora racemosa G. Mey., which grows along the banks of the River Butre, in the Western Region of Ghana. Chemical profiling using 1H-NMR and HRESI-LC-MS of fermentation extracts produced by the strain led to the isolation of the new compound, α-d-Glucopyranosyl-(1→2)-[6-O-(l-tryptophanyl)-β-d–fructofuranoside] or simply tortomycoglycoside (1). Compound 1 is an aminoglycoside consisting of a tryptophan moiety esterified to a disaccharide made up of β-d-fructofuranose and α-d-glucopyranose sugars. The full structure of 1 was determined using UV, IR, 1D, 2D-NMR and HRESI-LC-MS data. When tested against Trypanosoma brucei subsp. brucei, the parasite responsible for Human African Trypanosomiasis in sub-Saharan Africa, 1 (IC50 11.25 µM) was just as effective as Coptis japonica (Thunb.) Makino. (IC50 8.20 µM). The extract of Coptis japonica (Thunb.) Makino. is routinely used as laboratory standard due to its powerful antitrypanosomal activity. It is possible that, compound 1 interferes with the normal uptake and metabolism of tryptophan in the T. brucei subsp. brucei parasite.

Paenidigyamycin A, Potent Antiparasitic Imidazole Alkaloid from the Ghanaian Paenibacillus sp. DE2SH

A new alkaloid paenidigyamycin A (1) was obtained from the novel Ghanaian Paenibacillus sp. isolated from the mangrove rhizosphere soils of the Pterocarpus santalinoides tree growing in the wetlands of the Digya National Park, Ghana. Compound 1 was isolated on HPLC at tR = 37.0 min and its structure determined by MS, 1D, and 2D-NMR data. When tested against L. major, 1 (IC50 0.75 µM) was just as effective as amphotericin B (IC50 0.31 µM). Against L. donovani, 1 (IC50 7.02 µM) was twenty-two times less active than amphotericin B (IC50 0.32 µM), reinforcing the unique effectiveness of 1 against L. major. For T. brucei brucei, 1 (IC50 0.78 µM) was ten times more active than the laboratory standard Coptis japonica (IC50 8.20 µM). The IC50 of 9.08 µM for 1 against P. falciparum 3d7 compared to artesunate (IC50 36 nM) was not strong, but this result suggests the possibility of using the paenidigyamycin scaffold for the development of potent antimalarial drugs. Against cercariae, 1 showed high anticercaricidal activity compared to artesunate. The minimal lethal concentration (MLC) and minimal effective concentration (MEC) of the compound were 25 and 6.25 µM, respectively, while artesunate was needed in higher quantities to produce such results. However, 1 (IC50 > 100 µM) was not active against T. mobilensis.