Morphology, Anatomy and Secondary Metabolites Investigations of Premna odorata Blanco and Evaluation of Its Anti-Tuberculosis Activity Using In Vitro and In Silico Studies

In-depth botanical characterization was performed on Premna odorata Blanco (Lamiaceae) different organs for the first time. The leaves are opposite, hairy and green in color. Flowers possess fragrant aromatic odors and exist in inflorescences of 4–15 cm long corymbose cyme-type. In-depth morphological and anatomical characterization revealed the great resemblance to plants of the genus Premna and of the family Lamiaceae, such as the presence of glandular peltate trichomes and diacytic stomata. Additionally, most examined organs are characterized by non-glandular multicellular covering trichomes, acicular, and rhombic calcium oxalate crystals. P. odorata leaves n-hexane fraction revealed substantial anti-tuberculous potential versus Mycobacterium tuberculosis, showing a minimum inhibition concentration (MIC) of 100 μg/mL. Metabolic profiling of the n-hexane fraction using gas-chromatography coupled to mass spectrometry (GC/MS) analysis revealed 10 major compounds accounting for 93.01%, with trans-phytol constituting the major compound (24.06%). The virtual screening revealed that trans-phytol highly inhibited MTB C171Q receptor as M. tuberculosis KasA (β-ketoacyl synthases) with a high fitting score (∆G = −15.57 kcal/mol) approaching that of isoniazid and exceeding that of thiolactomycin, the co-crystallized ligand. Absorption, distribution, metabolism, excretion and toxicity predictions (ADME/TOPKAT) revealed that trans-phytol shows lower solubility and absorption levels when compared to thiolactomycin and isoniazid. Still, it is safer, causing no mutagenic or carcinogenic effects with higher lethal dose, which causes the death of 50% (LD50). Thus, it can be concluded that P. odorata can act as a source of lead entities to treat tuberculosis.

Micromorphological variations of trichomes in the genus Ocimum L.

Ocimum L. is an attractive fragrant ornamental plant with medicinal aromatic compounds. The study using digital microscopy revealed the distinct epidermal trichome morphology in five species of Ocimum including O. americanum L., O. basilicum L., O. gratissimum L., O. kilimandscharicum Gurke and O. tenuiflorum L. A distinguished variation in size, shape, type and abundance of trichomes on leaves and stem of all species are described and photographed. Both glandular and non-glandular trichomes scrutinized in all the species in which glandular type comprised capitate and peltate trichomes. On the stem, the longest glandular capitate trichome (GCT) and non-glandular trichome (NGT) were observed in O. tenuiflorum while O. basilicum possessed longest glandular peltate trichome (GPT). In case of foliar trichomes, the longest GCT observed on leaves of O. americanum; and O. basilicum showed the longest GPT and NGT. In the species, the septate or aseptate NGT possessed uni, bi or multicellular base with acute or broad apex. A distinguished variation in the number of cells in stalk and head of GT was observed in the study. Presence of silica bodies in peltate trichome of O. kilimandscharicum was noticed as the characteristic feature. Among the five species, the trichomes were abundant in O. kilimandscharicum; while O. basilicum showed sparse distribution. Trichomes with disrupted cells were also noted in O. americanum. Due to the presence of specific trichome characteristics, the efficient taxonomic key is prepared to identify the taxa at species level.

Mentha pulegium L.: A Plant Underestimated for Its Toxicity to Be Recovered from the Perspective of the Circular Economy

The aim of the study was to investigate the micromorphology of Mentha pulegium leaves and flowers harvested in three different Sicilian (Italy) areas with peculiar pedo-climatic conditions, and to characterize the phytochemical profile, the phytotoxic activity, and the eco-compatibility of their essential oils (EOs) for potential use as safe bioherbicides. Light microscopy (LM) and scanning electron microscopy (SEM) highlighted that M. pulegium indumentum consists of non-glandular and glandular trichomes of different types. Peltate trichomes of plants from the different sites showed few significant differences in dimension and abundance, but they were characterized by a surprisingly high number of secretory cells both in leaves and flowers. Phytochemical analyses showed that oxygenated monoterpenes were the most abundant class in all the EOs investigated (92.2–97.7%), but two different chemotypes, pulegone/isomenthone and piperitone/isomenthone, were found. The complex of morphological and phytochemical data indicates that soil salinity strongly affects the expression of the toxic metabolite pulegone, rather than the EO yield. Phytotoxicity tests showed a moderate activity of EOs against the selected species as confirmed by α-amylase assay. Moreover, the low toxicity on brine shrimp provided a rationale for the possible use of investigated EOs as eco-friendly herbicides.

Essential Oil Composition and Micromorphological Traits of Satureja montana L., S. subspicata Bartel ex Vis., and S. kitaibelii Wierzb. Ex Heuff. Plant Organs

The essential oil (EO) composition of Satureja plants is highly variable. Recent studies suggest that there is an even difference in the EO composition from different plant organs within the same plant. This study aims to examine the chemical profile of EOs and the micromorphological characteristics of different organs of three Satureja species. The relationship between the number of glandular trichomes and EOs profile and relative yield is also investigated. Individuals from five populations were visualized using a scanning electron microscope, while EOs of leaves, calyces, corollas, and whole aerial parts were isolated using simultaneous distillation and extraction and analyzed using gas chromatography/mass spectrometry. Three types of glandular trichomes were detected. Peltate trichomes were present on all plant organs of studied species, while two types of capitate trichomes show different organ and species preferences. The EOs profiles differed across the plant parts, but showed a species specific composition. Univariate and multivariate statistics were used to show a correlation between the peltate trichomes and EO yield, and chemophenetic significance of EO profiles.

Morphological and Anatomical Variations of Roots, Leaves, Peduncles, and Peduncle Bracts in the Vriesea oligantha Complex (Bromeliaceae): Perspectives for Taxonomy

Abstract—Vriesea is one of the genera of Bromeliaceae with the highest morphological diversity, including species of difficult recognition, many of them forming complexes, such as the Vriesea oligantha alliance. Morphological and anatomical comparative studies of vegetative and reproductive organs proved to be useful to solve such species complexes, besides indicating adaptive radiation. We analyzed comparatively the anatomy of roots, leaves, peduncles, and peduncle bracts of different populations found in rocky fields of Minas Gerais and Bahia, Brazil, with a taxonomic goal. In all the individuals studied the roots are composed of a velamen, a heterogeneous cortex, and a polyarch vascular cylinder, features that are common in the family. The leaves are covered by peltate trichomes and exhibit a hypodermis on both sides of the blade and a chlorenchyma composed of arm cells forming air lacunae between the collateral vascular bundles. The presence of subepidermal fiber strands in the leaves differentiates the populations of Minas Gerais from those of Bahia. The peduncle has an atactostele with compactly arranged cells in the cortex and pith. The peduncle bracts exhibit a greater number of peltate trichomes on the abaxial surface and secretory channels occur in the mesophyll. A cluster analysis (UPGMA) based on leaf morphology and tank channel diameter generated a dendrogram with four main clusters, which correspond to V. lancifolia, V. oligantha, and V. pseudoligantha, plus another taxon. Intraspecific variations in the color and margin shape of leaves and peduncle bracts are interpreted as adaptive responses to environmental factors, mainly luminosity.

More than Scales: Evidence for the Production and Exudation of Mucilage by the Peltate Trichomes of Tillandsia cyanea (Bromeliaceae: Tillandsioideae)

Bromeliad scales have been investigated extensively due to their recognition as a key ecological and evolutionary feature of Bromeliaceae. However, much remains unknown about such trichomes and only recently mucilage exudation was described for them in a species of the subfamily Bromelioideae. The present study aimed to investigate the secretion present in inflorescences of Tillandsia cyanea Linden ex K. Koch (Tillandsioideae) to determine whether the scales of this species also produce and release secretions. Samples of young and mature portions of inflorescences were collected and prepared according to standard methods for light and electron microscopy. Anatomical and ultrastructural results indicate that the secretion is produced by the wing portion of typical peltate trichomes on the adaxial surface of bracts. The secretory activity begins in the early stages of trichome expansion and characteristically occurs in cells exhibiting a porous cuticle and dense cytoplasm with numerous mitochondria and dictyosomes. Histochemical tests confirmed mucilage secretion and revealed proteins in the exudate. These data comprise the first record of mucilage exudation by trichomes within Tillandsioideae and indicate that this capacity may be more relevant to bromeliad biology than previously considered. Functional aspects and colleter-like activity are also discussed.

Trichome diversity studies in selected species of Sida

Sida (Family: Malvaceae) belongs to the genus of flowering plants that possess high medicinal value and is used traditionally in almost all parts of the world. There were about 18 species reported from the state of Kerala (India). Among these, some are with taxonomic controversies. Hence micro-morphological characters of leaves such as trichomes can be used as a taxonomic tool for the identification of plants. Their type, presence, absence and distribution are important diagnostic characters in plant identification and plant taxonomy. Plant samples were collected from different localities of Kerala. Foliar epidermal studies were carried out in order to identify the diversity and distribution of trichomes in the selected species of Sida viz., S. acuta, S. alnifolia, S. beddomei, S. cordata, S. cordifolia, S. fryxelli, S. ravii, S. rhombifolia and S. rhomboidea. Six types of trichomes were identified; they were stellate, conical, forked, capitate (short stalked), uniseriate multicellular and peltate. Stellate trichomes were observed in all the species. Conical trichomes were observed in S. beddomei, S cordata and S. fryxelli. Forked trichome was observed in S. acuta, S. cordata, S. cordifolia, S. ravii, S. rhombifolia and S. rhomboidea. Capitate (short stalked) trichomes were observed in S. acuta, S. alnifolia, S. rhombifolia and S. rhomboidea. Uniseriate multicellular trichomes were observed in S. cordifolia, S. fryxelli and S. ravii. Peltate trichomes are observed in all species except S. beddomei, S. cordifolia and S. fryxelli. However, these species could be easily distinguished by their conical trichomes. A bracketed dichotomous key was prepared for the identification of the species considered for the study.

SECRETORY STRUCTURES AND ESSENTIAL OIL COMPOSITION OF SELECTED INDUSTRIAL SPECIES OF LAMIACEAE

The objective of the study was to perform micromorphological analyses of the secretory structures of leaves and stems of oil-bearing industrial plants from the Lamiaceae family such as lemon balm (Melissa officinalis L.), peppermint (Mentha × piperita L.), sage (Salvia officinalis L.), marjoram (Origanum majorana L., syn. Origanum dubium Boiss.), rosemary (Rosmarinus officinalis L.) and common thyme (Thymus vulgaris L.) using light microscope and scanning electron microscope. In addition, an estimation of the content of volatile substances in the plant species under study was performed using GC-MS, as well as the qualitative and quantitative analysis of essential oil, that is an important component in terms of the estimation of raw material applicability for use in the industry. In the epidermal cells of studied plants, 2 types of Lamiaceae-type glandular trichomes were identified: short- and long-stalked capitate glandular trichomes with single- and bicellular secretory capitulum, and peltate glandular trichomes with eight- and over a dozen-cell secretory capitulum. Capitate trichomes were densely distributed on the surface of the epidermis, while peltate trichomes were sparse, though regular, and were situated in depressions. Glandular trichomes were found more frequently on leaves than on stems. The cuticle of the abaxial of leaf was characterized in most cases by the occurrence of larger average diameter peltate trichomes compared to the cuticle of the adaxial side of leaf. Peppermint produced the largest structures accumulating essential oil on the leaves (average diameter of peltate trichomes – 78.48 µm on the adaxial side of leaf, up to 96.43 µm), while on the stem, the highest average diameter of the peltate trichomes was observed in sage (an average of 75.53 µm, up to 85.99 µm). The lemon balm was characterized by the presence of capitate and peltate trichomes with the smallest diameter (an average of 44.26 µm). Lemon balm was characterized by the greatest density of glandular trichomes compared to other plant species. Among the plants studied, the highest content of oil was noted in the case of thyme and peppermint (2.22% and 2.20% v/w, respectively), and the lowest in green parts of lemon balm (0.17% v/w). The isolated essential oils contained predominantly components from the groups of monoterpenes and sesquiterpenes, and it is the presence of those substances that determines the possibility of utilizing the plants studied for a variety of purposes.