Thymus caespititius

Abstract: Twenty seven essential oils, isolated from plants representing 11 families of Portuguese flora, were screened for their nematicidal activity against the pinewood nematode (PWN), Bursaphelenchus xylophilus. The essential oils were isolated by hydrodistillation and the volatiles by distillation-extraction, and both were analysed by GC and GC-MS. High nematicidal activity was achieved with essential oils from Chamaespartium tridentatum, Origanum vulgare, Satureja montana, Thymbra capitata, and Thymus caespititius. All of these essential oils had an estimated minimum inhibitory concentration ranging between 0.097 and 0.374 mg/ml and a lethal concentration necessary to kill 100% of the population (LC100) between 0.858 and 1.984 mg/ml. Good nematicidal activity was also obtained with the essential oil from Cymbopogon citratus. The dominant components of the effective oils were 1-octen-3-ol (9%), n-nonanal, and linalool (both 7%) in C. tridentatum, geranial (43%), neral (29%), and β-myrcene (25%) in C. citratus, carvacrol (36% and 39%), γ-terpinene (24% and 40%), and p-cymene (14% and 7%) in O. vulgare and S. montana, respectively, and carvacrol (75% and 65%, respectively) in T. capitata and T. caespititius. The other essential oils obtained from Portuguese flora yielded weak or no activity. Five essential oils with nematicidal activity against PWN are reported for the first time.

Abstract: The identification, isolation and functional characterization of two genes encoding two monoterpene synthases—γ-terpinene synthase (Tctps2) and α-terpineol synthase (Tctps5)—from three chemically distinct Thymus caespititius (Lamiaceae) genotypes were performed. Genomic exon–intron structure was also determined for both terpene synthase genes, revealing an organization with seven exons and six introns. The cDNA of Tctps2 was 2,308 bp long and had an open reading frame of 1,794 bp encoding for a protein with 598 amino acids. Tctps5 was longer, mainly due to intron sequences, and presented high intraspecific variability on the plants analyzed. It encoded for a protein of 602 amino acids from an open reading frame of 1,806 bp comprising a total of 2,507 bp genomic sequence. The amino acid sequence of these two active Tctps genes shared 74 % pairwise identity, ranging between 42 and 94 % similarity with about 50 known terpene synthases of other Lamiaceae species. Gene expression revealed a multi-product Tctps2 and Tctps5 enzymes, producing γ-terpinene and α-terpineol as major components, respectively. These enzymatic results were consistent with the monoterpene profile present in T. caespititius field plants, suggesting a transcriptional regulation in leaves. Herewith reported for the first time for this species, these two newly characterized Tctps genes improve the understanding of the molecular mechanisms of reaction responsible for terpene biosynthesis and chemical diversity found in T. caespititius.

Abstract: Thymus herba-barona, Thymus pseudolanuginosus, and Thymus caespititius decoctions were screened for their phenolic constituents, along with their potential antioxidant, anti-inflammatory, and antibacterial activities. The total phenolic compounds in the extracts of the three plants ranged from 236.0 ± 26.6 mgGAE/g (T. caespititus) to 293.0 ± 30.5 mgGAE/g of extract (T. pseudolanuginosus), being particularly rich in caffeic acid derivatives, namely rosmarinic acid and its structural isomers, as well as flavones, such as luteolin-O-glucuronide. The T. pseudolanuginosus extract presented the best DPPH radical scavenging ability (EC50 = 10.9 ± 0.7 µg/mL), a high reducing power (EC50 = 32.2 ± 8.2 µg/mL), and effectively inhibited the oxidation of β-carotene (EC50 = 2.4 ± 0.2 µg/mL). The extracts also showed NO● scavenging activity close to that of ascorbic acid, and thus might be useful as anti-inflammatory agents. In addition, they exhibited antibacterial activity against gram-negative and gram-positive bacteria. Staphylococcus aureus strains were the most sensitive bacteria to thyme extracts, with minimum inhibitory concentration and minimum bactericidal concentration values in the range of 0.6-3.5 mg/mL. Overall, this work is an important contribution for the phytochemical characterization and the potential antioxidant, anti-inflammatory, and antimicrobial activities of these three Thymus species, which have been poorly explored.