Green Ultrasound Assisted Extraction of trans Rosmarinic Acid from Plectranthus scutellarioides (L.) R.Br. Leaves.

Duangjai Tungmunnithum,Laurine Garros,Sullivan Renouard,Samantha Drouet,Eric Lainé,Christophe Hano

doi:10.3390/plants8030050

Abstract

Painted nettle (Plectranthus scutellarioides (L.) R.Br.) is an ornamental plant belonging to Lamiaceae family, native of Asia. Its leaves constitute one of the richest sources of trans-rosmarinic acid, a well-known antioxidant and antimicrobial phenolic compound. These biological activities attract interest from the cosmetic industry and the demand for the development of green sustainable extraction processes. Here, we report on the optimization and validation of an ultrasound-assisted extraction (USAE) method using ethanol as solvent. Following preliminary single factor experiments, the identified limiting extraction parameters (i.e., ultrasound frequency, extraction duration, and ethanol concentration) were further optimized using a full factorial design approach. The method was then validated following the recommendations of the association of analytical communities (AOAC) to ensure the precision and accuracy of the method used to quantify trans-rosmarinic acid. Highest trans-rosmarinic acid content was obtained using pure ethanol as extraction solvent following a 45-minute extraction in an ultrasound bath operating at an ultrasound frequency of 30 kHz. The antioxidant (in vitro radical scavenging activity) and antimicrobial (directed toward Staphylococcus aureus ACTT6538) activities were significantly correlated with the trans-rosmarinic acid concentration of the extract evidencing that these key biological activities were retained following the extraction using this validated method. Under these conditions, 110.8 mg/g DW of trans-rosmarinic acid were extracted from lyophilized P. scutellarioides leaves as starting material evidencing the great potential of this renewable material for cosmetic applications. Comparison to other classical extraction methods evidenced a clear benefit of the present USAE method both in terms of yield and extraction duration.

Highlights

Plectranthus scutellarioides (L.) R.Br. or painted nettle (Figure 1a) is an ornamental and medicinal plant, mainly found in Asia, currently spread over America, Southern Africa, and Europe [1,2].Plants 2019, 8, 50; doi:10.3390/plants8030050 www.mdpi.com/journal/plantsPlants 2019, 8, x FOR PEER REVIEW synonym, Coleus blumei Benth.is well-known
Little attention has been paid to the optimization of its extraction from the leaves of this ornamental plant. This ornamental plant is known as easy to propagate by cuttings and high renewable biomass production of leaves can be obtained through basic horticultural approaches, the development of green extraction of rosmarinic acid (RA) using this raw starting material for potential cosmetic applications could be very promising
Many studies reported on RA production from P. scutellarioides using different biotechnological systems to improve its production from in planta using in vitro technologies, but little attention has been paid to the optimization of its extraction directly from the leaves of this ornamental plant

Summary

Introduction

Plectranthus scutellarioides (L.) R.Br. or painted nettle (Figure 1a) is an ornamental and medicinal plant, mainly found in Asia, currently spread over America, Southern Africa, and Europe [1,2].Plants 2019, 8, 50; doi:10.3390/plants8030050 www.mdpi.com/journal/plantsPlants 2019, 8, x FOR PEER REVIEW synonym, Coleus blumei Benth.is well-known. Plectranthus scutellarioides (L.) R.Br. or painted nettle (Figure 1a) is an ornamental and medicinal plant, mainly found in Asia, currently spread over America, Southern Africa, and Europe [1,2]. Plants 2019, 8, x FOR PEER REVIEW synonym, Coleus blumei Benth. Its synonym, This plantisisa aspecies speciesmember memberof ofthe the Lamiaceae. Widely cultivated cultivated as an ornamental ornamental plant plant due to the beauty of its leaves. Local local people people in in many many countries countries have have long long been been used used P. P. scutellarioides scutellarioides as as an herbal herbal medicine.

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