Phenolic Constituents of Lamium album L. subsp. album Flowers: Anatomical, Histochemical, and Phytochemical Study

Abstract

Flos Lamii albi has a high biological activity and is widely used in herbal medicine. The aim of the study was to characterize the secretory structures present in Lamium album subsp. album corolla and the location of phenolic compounds. Additionally, we carried out qualitative phytochemical analyses of flavonoids and phenolic acids. Light, fluorescence, and scanning electron microscopy were used to analyze the structure of the floral organs. The main classes of phenolic compounds and their localization were determined histochemically. Phytochemical analyses were performed with high-performance thin-layer chromatography (HPTLC) and high-performance liquid chromatography (HPLC). Six types of glandular trichomes were found which contained flavonoids, phenolic acids, and tannins. The phytochemical studies demonstrated the presence of caffeic, chlorogenic, ferulic, gallic, p-coumaric, protocatechuic, syringic, gentisic, and vanillic phenolic acids as well as rutoside, isoquercetin, and quercetin flavonoids. The corolla in L. album subsp. album has antioxidant properties due to the presence of various polyphenols, as shown by the histo- and phytochemical analyses. The distribution and morphology of trichomes and the content of phenolic compounds in the corolla have taxonomic, pharmacognostic, and practical importance, facilitating the identification of the raw material.

Histochemical and Phytochemical Analysis of Lamium album subsp. album L. Corolla: Essential Oil, Triterpenes, and Iridoids

“…As shown by our previous observations, short-stalked capitate trichomes with a 2-celled head in L. album flowers function non-synchronously [ 58 ]. The capitate trichomes located next to each other in L. album subsp.…”

“…Since we have not found such information in the literature so far, we present these data for the first time to fill the gap in the knowledge of this issue. Our previous study showed the presence of phenolic compounds: tannins, phenolic acids, and flavonoids in trichomes of this species [ 58 ]. The present study is a continuation and extension of our previous research.…”

“…Trichome morphotypes that were characteristic of L. album subsp. album flowers were distinguished and phenolic acids, flavonoids, and tannins were localized [ 58 ]. The petal and stamen indumentum comprised six types of glandular trichomes and two types of non-glandular trichomes.…”

“…The non-glandular trichomes on the corolla were represented by unicellular conical trichomes and 2–5-celled uniseriate unbranched trichomes. On the stamens, which constitute herbal material together with the corolla, long-stalked capitate trichomes and flattened single-celled mechanical trichomes were found [ 58 ].…”

“…However, there was no information about the identification and location of biologically active substances in the tissues of L. album flowers, which are a valuable medicinal and pharmaceutical raw material. In our previous study, were detected phenolic acids, flavonoids and tannins in the corollas of this species [ 58 ]. The present study is a continuation and extension of previous research and is now focused on other biologically active compounds.…”