Using acid-catalyzed degradation in the presence of cysteamine, the condensedtannins from Lithocarpus glaber leaves were characterized, following thiolysis, by meansof reversed-phase HPLC, 13C-NMR and matrix-assisted laser desorption/ionization time offlight mass spectrometry (MALDI-TOF MS) analyses. The thiolysis reaction productsshowed the presence of the procyanidin (PC) and prodelphinidin (PD) structures. The 13CNMRspectrum revealed that the condensed tannins were comprised of PD (72.4%) and PC(27.6%), and with a greater content of cis configuration rather than the trans configurationof C2–C3. The MALDI-TOF MS analysis proved the presence of PD units, and themaximum degree of polymerization (DP) was an undecamer. The antioxidant activity ofcondensed tannins from L. glaber leaves was evaluated by using a free radical scavengingactivity assay.

The antioxidant activity of Syzygium cumini leaf extracts was investigated usingthe 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging and ferric-reducingantioxidant power (FRAP) assays. The methanolic extract and its four water, ethyl acetate,chloroform, and n-hexane fractions were prepared and subjected to antioxidant evaluation.The results showed that the ethyl acetate fraction had stronger antioxidant activity than theother ones. HPLC data indicated that S. cumini leaf extracts contained phenoliccompounds, such as ferulic acid and catechin, responsible for their antioxidant activity. Asignificant linear relationship between antioxidant potency, free radical-scavenging abilityand the content of phenolic compounds of leaf extracts supported this observation.

The new diterpene methoxy-ent-8(14)-pimarenely-15-one (1) and three knownmetabolites: ent-8(14)-pimarene-15R,16-diol (2), stigmasterol (3) and β-sitosterol (4), wereisolated from the roots of the mangrove plant Ceriops tagal. Their structures and relativestereochemistry were elucidated by means of extensive NMR, IR and MS analysis.Compounds 1, 2, 3 and 4 exhibited significant antifouling activities against cyprid larvaeof the barnacle Balanus albicostatus Pilsbry, with EC50 values of 0.32±0.01, 0.04±0.00, 4.05±0.15 and 18.47±0.40 μg/cm2, respectively, whereas their toxicities towards cypridswere very low, with LC50 values all above 10μg/cm2.

Nitrogen and phosphorus dynamics during leaf development, senescence, anddecomposition of tall and dwarf forms of the red mangrove, Rhizophora mangleL., were studied in south Florida. Mature leaves of tall mangroves had significantlyhigher nitrogen (N) and phosphorus (P) concentrations than those of dwarf mangroves,which suggests that N and P are important factors associated with mangrovegrowth. Based on N:P ratios, both mangrove growth forms were P-limited, but dwarfmangroves were more so than tall mangroves. N and P were resorbed before leaf abscissionas evidenced by the decrease in leaf N and P concentrations during leaf senescence.Mangroves showing indications of greater P-limitation had significantlyhigher phosphorus resorption efficiencies and proficiencies (PRE and PRP, respectively).PRP, however, was more sensitive to the molar N:P ratio and the phosphorusconcentration of mature leaves than PRE. N and P immobilization was indicated bythe gradual increase in leaf N and P concentrations during leaf decomposition. Thisimmobilization could delay N and P leaching and loss from the detritus matrix andprovide plants with available N and P over a prolonged period of time.