Abstract
This study investigates the effects of various drying methods applied to leaves of Cistus creticus L. on the contents of polyphenols and the composition of the volatile fraction. The following four drying methods were used: convection drying at a temperature of 40 °C (CD 40 °C), 50 °C (CD 50 °C), and 60 °C (CD 60 °C); vacuum-microwave (VMD 240 W); combined drying, involving convection pre-drying (50 °C) and vacuum-microwave (240 W) finish drying (CPD-VMFD) as well as freeze-drying (FD). Polyphenols in the dried leaves were determined using chromatography-photodiode detector-quadrupole/time of flight-mass spectrometry (UPLC-PDA-Q/TOF-MS). The contents of odoriferous substances in the dry material were determined by means of head space-solid phase microextraction (HS-SPME) with the use of a gas chromatograph (GC). Thirty-seven polyphenol components including 21 flavonols, eight flavan-3-ols, and eight hydrolyzed tannins in dry Pink Rock Rose material were found for the first time. The highest contents of polyphenols, totaling 2.8 g 100 g−1 dry matter (d.m.), were found in the samples subjected to the CPD/VMFD drying method. Pink Rock Rose subjected to this drying method was characterized by large quantities of odoriferous compounds, mainly eugenol, thymol, and carvacrol, which contribute to its antiseptic properties. By using CPD/VMFD methods, it is possible to obtain fine quality dry material from the leaves of C. creticus.
Highlights
The Cistus, referred to as the rockrose, is a type of shrub growing in the Mediterranean region [1]
The UPLC-PDA-Q/TPF-MS technique permitted the identification of 37 polyphenol components including flavonols (21 components), flavan-3-ols, and hydrolyzed tannins (Table 1)
The amounts of polyphenols recorded in dried Cistus creticus samples after the FD to CPD/VMFD drying method were from 1.9 g 100 g−1 d.m. to 2.8 g 100 g−1 d.m
Summary
The Cistus (family Cistaceae), referred to as the rockrose, is a type of shrub growing in the Mediterranean region [1]. The plants classified in this genus are small coastal shrubs with pink or white flowers. They grow in very hot, sunny areas with calcareous soil as one of the degradation stages of evergreen forest plants [3]. Cistus plants are used in traditional folk medicine as anti-inflammatory, antiallergic, wound healing, antimicrobial, cytotoxic, and vasodilating agents. The beneficial properties of Cistus plants are mainly associated with the polyphenol content, compounds which are classified as strong antioxidants and radical scavengers [1]. Polyphenols inhibit the formation and development of inflammatory
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