• Seaweed extracts were profiled using LC-MS and GC–MS techniques. • Gracilaria fisheri showed the strongest anti-tyrosinase activity. • Docking revealed stigmasterol as a strong tyrosinase inhibitor. • Stigmasterol showed high safety, low toxicity, and good skin permeability. • First report of seaweed-derived stigmasterol for skin whitening use.

Lasianthus kailarsenii Poopath, Vajrodaya & Napiroon, L. tennissarimensis Napiroon, Balslev & Chayamarit and L. krabiensis Napiroon, Balslev & Chamchumroon are described as new species and illustrated. Lasianthus kailarsenii is morphologically close to L. lancilobus, but differs from it by its glabrous (not hirsute) branches and leaves, campanulate and glabrous (not obconical and hirsute) calyx, exserted (not included within the corolla tube) stigma, and 8 (not 4) pyrenes. Lasianthus tennissarimensis resembles L. robinsonii but differs from it by having lanceolate leaves that are 7.5-10 cm long (not oblong or oblong-elliptic, 12-16 cm long), its 5-6 (not 8-9) pairs of secondary veins, the calyx limbs that are narrowly lanceolate and 7-8 mm long (not linear and 2.5-4 mm long). Lasianthus krabiensis also resembles L. lancilobus but differs from it by having the abaxial leaf surface sparsely hirsute (glabrous), peduncle 1.5 mm (not 2.5-3 mm) long, and bracts shorter than calyx tube, 5-6 mm long (not longer than calyx tube, 1.5 cm long). Lasianthus oblongus which was previously known only from Peninsular Malaysia, has now been recorded in Yala (southern Thailand). A key that compares them to the related Thai Lasianthus species is also provided.

We describe Lasianthus ranongensis Sinbumr. & Napiroon as a new species in the genus Lasianthus. The new taxon is intensively discussed through taxonomic affinities and information on its habitat, distribution and conservation status is provided. Moreover, line drawings and stereo microscope images of important fertile organs are demonstrated. The new species is morphologically similar to L. stipularis but differs in its having flattened branches (vs. terete), leaf blade elliptic-oblong shape of 15.0–20.0 × 4.0–6.0 cm (vs. oblanceolate-oblong 12.0–16.0 × 3.0–5.5 cm), 9–12 pairs of veins (vs. 9–10 pairs), stipule 5–7 mm long, half covering cymes (vs. 10–12.5 mm long, entirely covering cymes), four or five bracts narrowly lanceolate, 2.5–3.0 mm long (vs. bracts numerous, broadly triangular, 10–15 mm), flowers with cupular calyx (vs. with campanulate calyx), corolla villous on internal surface, and six or seven lobed (vs. pubescent on internal surface and four lobed) and drupes with five pyrenes (vs. with four pyrenes). It is also similar to L. pseudo-stipularis, but from which it is obviously distinguished by its stipule half covers cymes, secondary veins have 9–12 pairs of secondary veins, cupular calyx shape, six or seven lobed corolla, and drupe with five pyrenes, whereas L. pseudo-stipularis has stipule entirely covering cymes, 7–8 pairs of secondary veins, obconic calyx, four lobed corolla, and drupe with four pyrenes.

Aim: To evaluate the activity of medicinal Lasianthus extracts on bacteria and to determine the chemical characters among three medicinal Lasianthus (Rubiaceae) species. Materials and Methods: The phytochemical investigation of L. cyanocarpus, L. hirsutus and L. lucidus were performed using thin layer chromatography and high performance liquid chromatography (HPLC) techniques. Four antibacterial resistant strains including Staphylococcus aureus ATCC 43300 (MRSA), Klebsiella pneumoniae ATCC BAA 1705 (carbapenemase; KPC-producing strain) and Pseudomonas aeruginosa ATCC 27853 (AmpC β-lactamase producing strain) were used. The phytochemical investigation of L. cyanocarpus, L. hirsutus and L. lucidus were performed using thin layer chromatography and high performance liquid chromatography (HPLC) techniques. We also detected the effects of extracts on bacteria by using a scanning electron microscope. Results: The lipophilic extracts from the three plants revealed the terpenoids, coumarin and iridoid. HPLC showed similarities in the chemical profiles of both leaf and stem bark extracts. L. lucidus lipophilic extracts revealed the greatest effect against S. aureus and P. aeruginosa at 400 and 100 μg/mL respectively, whereas L. cyanocarpus extracts prominently affected K. pneumoniae at 400 μg/mL. Cell lysis and leakage of bacteria treated with extracts were observed. Conclusion: Our findings surprisingly showed the potential of antibacterial effect among resistant pathogenic bacteria. We also revealed the comparable signals of the chemical characters from the three Lasianthus. These findings support the traditional use related infectious diseases and it might be possible to further develop the antibiotic agents. Keywords Resistant bacteria; Lasianthus; Ethnomedicine; Infectious diseases

Background: Scopoletin, a compound abundant in Rubiaceae such as Lasianthus lucidus and Morinda citrifolia , has demonstrated various activities, including antimicrobial activity, antinociceptive properties or pain relief and effects on cancer cell lines. Accordingly, it has significant potential as a precursor for synthetic bioactive agents for reducing pain such its derivative includes benzene ring. However, very little has been reported regarding normal cellular effects or human skin irritation of such synthetic compounds, knowledge which is necessary if they are to be further developed. Thus, the aim of this study was to isolate scopoletin from Thai Rubiaceae, synthesize a derivative, and test its cytotoxicity. Materials and Methods: Stem bark of L. lucidus and fruits of M. citrifolia were extracted and the extract partitioned into hydrophilic and lipophilic fractions. Lipophilic extracts were further fractionated by column chromatography and analysed by High-Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD). Purified scopoletin was used for the synthesis of its benzoate derivative and their structures were confirmed with the help of Nuclear Magnetic Resonance (NMR) spectroscopy. The cytotoxicity of the derivative compound was tested in the immortalized human keratinocyte HaCaT cell line. Results: The lipophilic extracts displayed scopoletin contents of 16.14% and 13.94%, respectively. Scopoletin was completely converted to a target derivative, 6-methoxy-2-oxo-4a,8a-dihydro-2H-chromen-7-yl benzoate. This compound exhibited an IC ₅₀ value of 182.95 ± 6.15 µg/mL, with cell viability increased at concentrations less than 15.63 µg/mL but decreased at concentrations of 31.25 to 500 µg/mL. Conclusions: We completely actualized both isolation and synthesis to achieve a high yield of the target scopoletin and benzoylscopoletin. The cytotoxicity evidence obtained from this study supports the establishment of safe dosage limits, which have not been previously reported. This finding provides a scientific basis for further drug development. The analyses demonstrate reproducible isolation of scopoletin and synthesis of the derivative.