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

Abstract

The aim of this study was to conduct a histochemical analysis to localize lipids, terpenes, essential oil, and iridoids in the trichomes of the L. album subsp. album corolla. Morphometric examinations of individual trichome types were performed. Light and scanning electron microscopy techniques were used to show the micromorphology and localization of lipophilic compounds and iridoids in secretory trichomes with the use of histochemical tests. Additionally, the content of essential oil and its components were determined using gas chromatography-mass spectrometry (GC-MS). Qualitative analyses of triterpenes carried out using high-performance thin-layer chromatography (HPTLC) coupled with densitometric detection, and the iridoid content expressed as aucubin was examined with spectrophotometric techniques. We showed the presence of iridoids and different lipophilic compounds in papillae and glandular and non-glandular trichomes. On average, the flowers of L. album subsp. album yielded 0.04 mL/kg of essential oil, which was dominated by aldehydes, sesquiterpenes, and alkanes. The extract of the L. album subsp. album corolla contained 1.5 × 10−3 ± 4.3 × 10−4 mg/mL of iridoid aucubin and three triterpenes: oleanolic acid, β-amyrin, and β-amyrin acetate. Aucubin and β-amyrin acetate were detected for the first time. We suggest the use of L. album subsp. album flowers as supplements in human nutrition.

Morphoanatomical, Histochemical, and Essential Oil Composition of the Plectranthus ornatus Codd. (Lamiaceae)

“…However, there is a difference in lipidic composition, as evidenced by the Nadi reagent. This reaction stained purplish, indicating terpenes of different sizes (molecular masses), implicating a mixture of essential oil and resin [ 31 ]. The terpene identification is more effective when the reaction happens (positive result), as seen in this study and also in previous works with P. amboinicus, Mentha x villosa Huds [ 18 , 32 ].…”

“…However, there is a difference in lipidic composition, as evidenced by the Nadi reagent. This reaction stained purplish, indicating terpenes of different sizes (molecular masses), implicating a mixture of essential oil and resin [31]. The terpene The trichome secretions of Plectranthus ornatus reacted (positive result) for total lipids and acidic lipids.…”

Localization of Sesquiterpene Lactones Biosynthesis in Flowers of Arnica Taxa

“…The ability to synthesize lipids and polyphenols in Inula helenium covering hears tissues was noted by [70], who believed that in addition to their protective role, trichomes may have a secretory function, which was evident after histochemical assays [71]. Since then, there have been a growing number of reports on new functions beyond the physical protection of non-glandular trichomes connected to the chemical interactions of plants with the environment, supplementary to glandular trichomes [72,73]; however, [74] stated that the volatile terpene compound content in Chrysanemum leaves was significantly correlated with the density of glandular trichomes but not with the T-shape covering trichomes. This finding supports the hypothesis that glandular trichomes are responsible for the emission of volatile terpenes.…”

Use of Secondary Metabolites Profiling and Antioxidant Activity to Unravel the Differences between Two Species of Nettle

“…To highlight the presence of iridoids in the analyzed extracts, two different derivatization reagents were used: the Ehrlich reagent and anisaldehyde solution. The reagents were prepared as follows: Ehrlich reagent-0.5 g of p-(dimethylamino)benzaldehyde were solved in 150 mL of methanol and 50 mL of concentrated HCl; and the anisaldehyde solution-170 mL of methanol was mixed with 20 mL of acetic acid and 10 mL of sulfuric acid, over which 1 mL of anisaldehyde was added [27]. The eluted and dried chromatographic plates were separately sprayed with each reagent and heated for 5 min at 100 • C. The iridoids were detected as blue-grey spots on a pink background in the case of the Ehrlich reagent and blue-violet on a yellow background in the case of anisaldehyde.…”