Anti-inflammatory effects of orally and topically administered nanoformulations of Malva parviflora root extracts, and Prunus persica and Cupressus sempervirens exudates

Background

Medicinal plants have been used traditionally as oral and topical herbs for treating inflammation and alleviating pain. Particularly in traditional Chinese medicine (TCM) practices, many plants from the genera Malva, Prunus, and Cupressus are used to treat various inflammation-related diseases. This study investigated in vitro and in vivo anti-inflammatory activity of the root extracts of Malva parviflora, the exudates of Prunus persica, Cupressus sempervirens and their chitosan nanoparticles and chitosan nanogels.

Methods

In vitro anti-inflammatory activities of M. parviflora root extracts, P. persica and C. sempervirens exudates were investigated using the protein denaturation assay method. A 1% bovine albumin reaction mixture in phosphate buffer and 80% (v/v) methanol was incubated with plant extracts or exudates at 37 °C and 70 °C. Cross-linked chitosan nanoparticles loaded with plant extracts or exudates were prepared by the gelation method. The entrapment efficiency of the plants in the chitosan nanoformulation was estimated using the phenolic content of plant materials. The nanoparticles-based nanogel was formulated by suspending nanoparticles in a gel base. Inflammation was induced in Wistar rats (230 – 270 g) by subcutaneous injection of 0.1 mL of 1% (w/v) carrageenan in the plantar tissue of the right hind paw of the rats. The rats (n = 48) were randomly divided into two experimental groups (A and B) of 24 rats each for oral and topical administration of nanoformulations, respectively. Each group (n = 24) was subdivided into 6 test group (n = 4), where test groups 1, 2, and 3 were treated with 500 mg/kg/BW each of M. parviflora, C. sempervirens, and P. persica nanoparticle/nanogel, either orally or topically, respectively. Test groups 4, 5, and 6, respectively served as positive control, placebo nanoparticles (i.e., chitosan nanoparticles), and negative control, treated orally or topically with indomethacin (50 mg/kg/BW), chitosan nanoparticle/nanogel alone (500 mg/kg/BW/100 mg/kg/BW), and saline (3 mL).

Results

P. persica exudate had the highest TPC of 70.42 ± 0.53 µg of GAE/mg compared to M. parviflora root extract and C. sempervirens exudate with the 30.93 ± 1.65 µg of GAE/mg and 9.99 ± 0.65 µg of GAE/mg, respectively. M. parviflora root extracts had the highest in vitro protein denaturation (92.40%) compared to leaves and stem extracts. P. persica and C. sempervirens nanoparticles had the highest entrapment efficiencies (99.46% and 99.56%). M. parviflora root extract nanoparticles showed the greatest inhibition of oedema (90%) with oral administration, outperforming P. persica and C. sempervirens exudates nanoparticles (both 87%). M. parviflora, P. persica and C. sempervirens nanoparticles and placebos (chitosan) nanoparticles had better overall anti-inflammatory activity than indomethacin after 24 h. For topical applications, C. sempervirens exudate nanogel had the highest oedema inhibition, and placebo nanogel was more effective than the other plant nanogels and indomethacin after 24 h.

Conclusion

Formulating medicinal plants in nanoscale dosage forms provides an effective therapy against inflammation. This avenue could counteract the rapidly developing resistance of drugs to diseases and some side effects associated with the administration of multiple allopathic drugs. Further in vivo studies using steroidal and non-steroidal anti-inflammatory controls are recommended.