RESUMEN
Three new Mitrephora species (Annonaceae), M.langsuanensis sp. nov., M.sirindhorniae sp. nov. and M.sukhothaiensis sp. nov., are described from Thailand. Mitrephoralangsuanensis resembles M.macclurei, but its leaves have more secondary veins, and its flowers have more carpels, with yellow-and-pink striped outer petals with a margin that becomes undulate with age. Mitrephorasirindhorniae resembles M.tomentosa, but has larger sepals and petals, longer flowering pedicels, and shorter monocarp stipes, with monocarps that have a longitudinal ridge. Mitrephorasukhothaiensis is distinct from its Thai congeners in having outer petals that reflex at maturity and inner petals with a pair of appendages on the margin adaxially. The addition of these three new taxa raises the total number of Mitrephora species in Thailand to 14. An identification key for Thai species is provided.
RESUMEN
Two new Goniothalamus species (Annonaceae), G.roseipetalus sp. nov. and G.sukhirinensis sp. nov., are described from the southern limits of Peninsular Thailand (Narathiwat and Yala Provinces). Both new species resemble G.macrophyllus, G.scortechinii and G.uvarioides. The addition of these two new species brings the total number of Goniothalamus species in Thailand to 27. Separate identification keys are provided for flowering and fruiting specimens of the Thai species.
RESUMEN
A new species, Mitrephoramonocarpa R.M.K.Saunders & Chalermglin, sp. nov. (Annonaceae), is described from Surat Thani Province in Peninsular Thailand. It resembles two other species, M.alba Ridl. and M.keithii Ridl., with which it is broadly sympatric, but can be distinguished by its solitary flowers (not borne in thyrsoid inflorescences as in most other Mitrephora species), single carpel per flower (and hence single monocarp per fruit) and the lack of a monocarp stipe. A key to the nine Mitrephora species in Thailand is provided.
RESUMEN
Two new species of Artabotrys are described from Thailand. Artabotrys tanaosriensis J.Chen, Chalermglin & R.M.K.Saunders, sp. nov., is similar to A. oblanceolatus Craib but differs in its symmetrical, cuneate or decurrent leaf base, externally distinct outer petal blades and claws, deltoid and undulate outer petal blades, rhomboid and undulate inner petal blades and shorter, subsessile and slightly beaked monocarps. Artabotrys spathulatus J.Chen, Chalermglin & R.M.K.Saunders, sp. nov., is most similar to A. tanaosriensis but differs in having flat outer petal blades, broadly rhomboid outer petal claws, broadly spathulate and strongly concave inner petal blades and strongly beaked monocarps. Two new records for the Flora of Thailand are furthermore reported here: A. punctulatus C.Y.Wu ex S.H.Yuan and A. byrsophyllus I.M.Turner & Utteridge, which were previously confused with A. aeneus Ast and A. grandifolius King, respectively. A key to Artabotrys species indigenous to Thailand is provided here.
RESUMEN
Four dimeric chalcone derivatives, 8â³,9â³-dihydrowelwitschin H, uvarins A-C, a naphthalene derivative, 2-hydroxy-3-methoxy-6-(4'- hydroxyphenyl)naphthalene, and the known dimeric chalcones, dependensin and welwitschin E, flavonoids, a cyclohexane oxide derivative, an aromatic aldehyde were isolated from the roots of Uvaria siamensis (Annonaceae). The structures of the compounds were elucidated by spectroscopic analysis, as well as by comparison with literature data. The isolated compounds with a sufficient amount for biological assays were evaluated for their antimalarial, antimycobacterial, and cytotoxic activities. The dimeric chalcones 8â³,9â³-dihydrowelwitschin H, uvarins B and C, dependensin and welwitschin E showed strong antiplasmodial activity with IC50 values of 3.10, 3.02, 3.09, 4.21 and 3.99 µg/mL, respectively. A possible biosynthesis pathway of the dimeric chalcones is discussed.
