Chemical composition of Mentha pulegium L. (Pennyroyal) plant as influenced by foliar application of different sources of zinc

Abstract

Background and objective Mentha pulegium L. is commonly known as pennyroyal and it is highly aromatic than any other mint. The essential oil could be considered as a possible candidate for human cancer chemotherapy. This study was carried out to evaluate the effect of different sources of zinc (algae extract, zinc sulfate, zinc multi, and zinc chelated) on herb yield, nutrient contents and their uptake, carbonic anhydrase, and essential oil production of M. pulegium plant. Materials and methods A field experiment was carried out under drip irrigated sandy soil at the Experimental Station of National Research Centre in Nubaria district, El-Behira Governorate, Egypt. Macronutrients and micronutrients contents of herb, nutrient uptake, carbonic anhydrase activity, and essential oil content were determined. Essential oil constituents were analyzed by chromatography-mass spectrometry. Results The results showed that algae extract followed by zinc multi significantly increased herb fresh and dry weight yield, nutrients content and their uptake, as well as showed the stimulatory impact on carboxylation enzyme activities. The highest essential oil yield (0.93 ml/plant and 20.67 l/ha) was recorded with algae extract, followed by zinc multi (0.80 ml/plant and 17.78 l/ha) than zinc chelate (0.50 ml/plant and 11.11 l/ha). Chromatography-mass spectrometry analyses of the essential oil showed that the essential oil composition was characterized by a high percentage of oxygenated compounds (96.83–97.33%) while the nonoxygenated compounds ranged from 2.48 to 2.89%. The major constituents of oxygenated compounds were found to be pulegone (67.75–74.43%) followed by neomenthone (10.66–17.12%). Algae extract and zinc multi produced the highest relative concentration of neomenthone (17.12 and 16.72%) and the lowest concentration of pulegone (67.75 and 67.97%). In contrast, foliar application of zinc chelated and zinc sulfate increased the biosynthesis of pulegone (74.43 and 73.98%) and decreased the percent of neomenthone (11.39 and 10.66%). Conclusion It might be concluded that the foliar application of zinc as algae extract followed by zinc multi chelated gave remarkable higher increases in herb yield, nutrients content and their uptake, carbonic anhydrase and essential oil production of M. pulegium plant.