Differential Response of the Photosynthetic Machinery to Fluctuating Light in Mature and Young Leaves of Dendrobium officinale.

A key component of photosynthetic electron transport chain, photosystem I (PSI), is susceptible to the fluctuating light (FL) in angiosperms. Cyclic electron flow (CEF) around PSI and water-water cycle (WWC) are both used by the epiphytic orchid Dendrobium officinale to protect PSI under FL. This study examined whether the ontogenetic stage of leaf has an impact on the photoprotective mechanisms dealing with FL. Thus, chlorophyll fluorescence and P700 signals under FL were measured in D. officinale young and mature leaves. Upon transition from dark to actinic light, a rapid re-oxidation of P700 was observed in mature leaves but disappeared in young leaves, indicating that WWC existed in mature leaves but was lacking in young leaves. After shifting from low to high light, PSI over-reduction was clearly missing in mature leaves. By comparison, young leaves showed a transient PSI over-reduction within the first 30 s, which was accompanied with highly activation of CEF. Therefore, the effect of FL on PSI redox state depends on the leaf ontogenetic stage. In mature leaves, WWC is employed to avoid PSI over-reduction. In young leaves, CEF around PSI is enhanced to compensate for the lack of WWC and thus to prevent an uncontrolled PSI over-reduction induced by FL.

Triterpene-farnesyl hydroquinone conjugates from Ganoderma calidophilum.

Two new lanostane-type triterpenoids characterized with farnesyl hydroquinone moieties, ganocalidoins A (1) and B (2), were isolated from the fruiting body of Ganoderma calidophilum, together with two known tripterpenes (3-4). The structures of compounds 1 and 2 were determined by extensive spectroscopic data including HRESIMS, 1D and 2D NMR. Ganocalidoins A and B showed anti-oxidant capacity with IC50 values of 38.7 ± 2.8 and 34.2 ± 1.8 µM, respectively. The compounds did not show tyrosinase inhibition activity.

Terpenes isolated from Polyalthia simiarum and their cytotoxic activities.

Two new C31 triterpenes, polysimiaric acid A (1) and B (2) as well as one new clerodane diterpenoid, 16,16-dimethoxy-cleroda-3,13Z-dien-15-oic acid (3), together with six known compounds were isolated from Polyalthia simiarum. Their structures were determined by analysis of 1D and 2D NMR data. Three new compounds were tested for their cytotoxicity against five human tumour cell lines. Compound 3 showed cytotoxic activities against SMMC-7721 with the IC50 value of 22.43 µM.

Amides and neolignans from the aerial parts of Piper bonii.

Six amides, piperbonamides A-F, three neolignans piperbonins A-C, and 11 known compounds were isolated from the aerial parts of Piper bonii (Piperaceae). The structures of piperbonamides A-F and piperbonins A-C were elucidated based on the analysis of 1D and 2D NMR and MS data. Piperbonin A, (+)-trans-acuminatin, (+)-cis-acuminatin, (+)-kadsurenone, and pipernonaline showed weak activity against platelet aggregation with IC50 values of 118.2, 108.5, 90.02, 107.3, and 116.3 µM, respectively, as compared with the positive control, tirofiban, with an IC50 value of 5.24 µM. Piperbonamides A-F were inactive against five tumor cell lines at concentrations up to 40 µM.

Neolignans from Selaginella moellendorffii.

Two new neolignans selaginellol (1) and selaginellol 4'-O-ß-D-glucopyranoside (2), together with seven known compounds (3-9), were isolated from the whole plant of Selaginella moellendorffii. The structures of the new isolates were determined through spectroscopic data analysis. Compounds 1-9, as well as compounds 10-18 previously isolated from the species, were measured for the activity against platelet aggregation induced by ADP or collagen. Three neoligans (8, 11, and 12), one flavanone (14), and one alkaloid (16) showed inhibitory activity against ADP- or collagen-induced platelet aggregation as compared with tirofiban. The dihydrobenzofuran neolignans (8, 11, and 12) are more potent than the benzofuran neolignan (13) and other types of neolignans (1-7). Glucosidation of the dihydrobenzofuran neolignans (11 and 12) is helpful for the activity. Two new neolignans selaginellol (1) and selaginellol 4'-O-ß-D-glucopyranoside (2) were isolated from the whole plant of Selaginella moellendorffii. Several compounds from this plant showed the activity against platelet aggregation induced by ADP or collagen.

Palladium-catalyzed unactivated C(sp3)-H bond activation and intramolecular amination of carboxamides: a new approach to ß-lactams.

An efficient method to synthesize the ß-lactams with high regioselectivity via Pd-catalyzed C(sp(3))-H bond activation and intramolecular amination of simple and readily available aminoquinoline carboxamides was demonstrated. C6F5I plays a significant role in the formation of the C-N bond of the four-membered ring ß-lactams. High yield along with wide substrate scope and functional group tolerance makes this reaction applicable to build natural-product-derived ß-lactams. This method has been applied to the efficient synthesis of the ß-lactamase inhibitor MK-8712.

Asymmetric Michael/cyclization tandem reaction of 4-hydroxycoumarin with ß-nitroalkenes catalyzed by chiral bifunctional thioureas.

The first asymmetric Michael/cyclization tandem reaction of 4-hydroxycoumarin with nitroolefins catalyzed by chiral bifunctional thioureas was reported and 2,3-dihydrofuro[3,2-c]-coumarin adducts have been obtained in moderate yields (53-75%) and good enantioselectivities (64-90% ee).

Antioxidant phenolics from Broussonetia papyrifera fruits.

Fractionation of the EtOH extract from the fruits of Broussonetia papyrifera led to the isolation of 15 phenolic compounds (1-15). Their structures were identified using spectroscopic methods. Among these compounds, 1 and 2 are new and 3-15 were isolated from this plant for the first time. Antioxidant activities of compounds 2-15 against H(2)O(2)-induced injury in SY5Y cells and 1,1-diphenyl-2-picrylhydrazyl radical scavenging activities were evaluated.

Antioxidant Lignans from the Fruits of Broussonetia papyrifera.

Nine new lignans, chushizisins A-I (1-9), and three known lignans, threo-1-(4-hydroxy-3-methoxyphenyl)-2-{4-[(E)-3-hydroxy-1-propenyl]-2-methoxyphenoxy}-1,3-propanediol (10), erythro-1-(4-hydroxy-3-methoxyphenyl)-2-{4-[(E)-3-hydroxy-1-propenyl]-2-methoxyphenoxy}-1,3-propanediol (11), and 3-[2-(4- hydroxyphenyl)-3-hydroxymethyl-2,3-dihydro-1-benzofuran-5-yl]propan-1-ol (12), were isolated from the fruits of Broussonetia papyrifera. Their structures were elucidated using spectroscopic methods. Compounds 1, 5, 6, 8, 9, and 11 exhibited antioxidant activities against H(2)O(2)-induced impairment in PC12 cells, while compounds 1, 2, 4, 7, and 11 showed DPPH radical-scavenging activities with IC(50) values of 236.8, 156.3, 273.9, 281.1, and 60.9 microM, respectively.