Influence of Comminution Methods and Air Exposure in the Production of Melissa officinalis Mother Tincture.

INTRODUCTION: During the processing of fresh plants, prolonged exposure to the air can cause rapid oxidative changes, and this is further accelerated if they have large surface areas. These changes can ultimately lead to losses in valuable ingredients and deterioration of the final product. Consequently, in the food, cosmetics, and pharmaceutical industries, oxidation and the use of antioxidant conservatives are major considerations during processing and production. However, similar considerations are not currently made for herbal medicines. The differences in the UV-Vis spectra of several commercial herbal mother tinctures were investigated here to determine if the oxidation process occurred and should thus be considered during their production. METHODS: The impact of air exposure on comminuted fresh Melissa officinalis and on the quality of the resulting mother tincture was evaluated using UV-Vis spectrophotometric analysis, antioxidant tests (potassium permanganate and FOLIN-Ciocalteu), and high-performance thin-layer chromatography. RESULTS: A time-dependent decrease in phenolic compounds, UV absorbance, and antioxidant capacity of the Melissa officinalis mother tincture were observed. Specifically, the antioxidant capacity of ground Melissa officinalis in the resulting herbal mother tincture was reduced by 40.47% and 55.52% after 5 and 30 min of air exposure, respectively. CONCLUSIONS: The results indicate that the Melissa officinalis mother tincture is affected if its comminuted starting material is exposed to air during the manufacturing process and that this should be considered when producing fresh herbal medicine plant products in the future.

Synthesis and Structure-Activity Relationship Studies of C2-Modified Analogs of the Antimycobacterial Natural Product Pyridomycin.

A series of derivatives of the antimycobacterial natural product pyridomycin have been prepared with the C2 side chain attached to the macrocyclic core structure by a C-C single bond, in place of the synthetically more demanding enol ester double bond found in the natural product. Hydrophobic C2 substituents of sufficient size generally provide for potent anti-Mtb activity of these dihydropyridomycins (minimum inhibitory concentration (MIC) values around 2.5 µM), with several analogs thus approaching the activity of natural pyridomycin. Surprisingly, some of these compounds, in contrast to pyridomycin, are insensitive to overexpression of InhA in Mycobacterium tuberculosis (Mtb). This indicates that their anti-Mtb activity does not critically depend on the inhibition of InhA and that their overall mode of action may differ from that of the original natural product lead.