Browsing by Author "Becerra, Jose"

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    Explaining differential herbivory in sun and shade: the case of Aristotelia chilensis saplings
    (2010) Guerra, Patricia C.; Becerra, Jose; Gianoli, Ernesto
    Differential herbivory in contrasting environments is commonly explained by differences in plant traits. When several plant traits are considered, separate correlation analyses between herbivory and candidate traits are typically conducted. This makes it difficult to discern which trait best explain the herbivory patterns, or to avoid spurious inferences due to correlated characters. Aristotelia chilensis saplings sustain greater herbivory in shaded environments than in open habitats. We measured alkaloids, phenolics, trichomes, leaf thickness and water content in the same plants sampled for herbivory. We conducted a multiple regression analysis to estimate the relationship between herbivory and each plant trait accounting for the effect of correlated traits, thus identifying which trait(s) better explain(s) the differential herbivory on A. chilensis. We also estimated insect abundance in both light environments. Palatability bioassays tested whether leaf consumption by the main herbivore on A. chilensis was consistent with field herbivory patterns. Overall insect abundance was similar in open and shaded environments. While saplings in open environments had thicker leaves, lower leaf water content, and higher concentration of alkaloids and phenolics, no difference in trichome density was detected. The multiple regression analysis showed that leaf thickness was the only trait significantly associated with herbivory. Thicker leaves received less damage by herbivores. Sawfly larvae consumed more leaf tissue when fed on shade leaves. This result is consistent with field herbivory and, together with results of insect abundance, renders unlikely that the differential herbivory in A. chilensis was due to greater herbivory pressure in open habitats.
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    ISOLATED LIGNANS OF ARAUCARIA ARAUCANA (MOLINA) K. KOCH PROVIDE WOOD PROTECTION AGAINST ATTACK BY THE XYLOPHAGOUS FUNGUS PLEUROTUS OSTREATUS (JACQ.) P. KUMM
    (2023) Bravo-Arrepol, Gaston; Torres, Solange; Perez, Claudia; Gonzalez-Ramirez, Mariela; Figueroa, Fabian; Cabrera-Barjas, Gustavo; Aranda, Mario; Tiezzi, Antonio; Gavin, Jose; Paz, Cristian; Becerra, Jose
    Araucaria araucana (Molina) K. Koch is an evergreen conifer endemic of Southern Chile and it is considered a sacred tree by the Pehuenche originary people. A. araucana is endangered in the red book. The knots wood of A. araucana are resistant to biological degradation, due to producing a high amount of lignans, even after the decomposition of the tree is possible to find its knots in the forest. In the present study the chemical composition of three wood tissue of A. araucana; knotwood, stemwood, and branches were analyzed by HPTLC-MS, GC-MS, and NMR. Three lignans were purified and identified as eudesmin (1), ((1S,2R,3R) 1,2,3,4tetrahydrona phthalene-2,3-diyl) dimethanol (2) and secoisolarisiresinol (3). Folin-Ciocalteu, DPPH and resistance to biodegradation assays were evaluated to extracts from compressed wood zones. Eudesmin was identified as the principal lignan in knots with a 0.5%w/w and outperformed the fungicide Nipacide (R) P511 in protecting wood against xylophage fungi Pleurotus ostreatus (Jacq.) P. Kumm.
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    Sulfated Polysaccharide Extracted from the Green Algae Codium bernabei: Physicochemical Characterization and Antioxidant, Anticoagulant and Antitumor Activity
    (2022) Figueroa, Fabian A.; Abdala-Diaz, Roberto T.; Perez, Claudia; Casas-Arrojo, Virginia; Nesic, Aleksandra; Tapia, Cecilia; Duran, Carla; Valdes, Oscar; Parra, Carolina; Bravo-Arrepol, Gaston; Soto, Luis; Becerra, Jose; Cabrera-Barjas, Gustavo
    Codium bernabei is a green alga that grows on Chilean coasts. The composition of its structural polysaccharides is still unknown. Hence, the aim of this work is to isolate and characterize the hot water extracted polysaccharide fractions. For this purpose, the water extracts were further precipitated in alcohol (TPs) and acid media (APs), respectively. Both fractions were characterized using different physicochemical techniques such as GC-MS, GPC, FTIR, TGA, and SEM. It is confirmed that the extracted fractions are mainly made of sulfated galactan unit, with a degree of sulfation of 19.3% (TPs) and 17.4% (ATs) and a protein content of 3.5% in APs and 15.6% in TPs. Other neutral sugars such as xylose, glucose, galactose, fucose, mannose, and arabinose were found in a molar ratio (0.05:0.6:1.0:0.02:0.14:0.11) for TPs and (0.05:0.31:1.0:0.03:0.1:0.13) for ATs. The molecular weight of the polysaccharide samples was lower than 20 kDa. Both polysaccharides were thermally stable (Tonset > 190 degrees C) and showed antioxidant activity according to the ABTS(center dot+) and DPPH tests, where TPs fractions had higher scavenging activity (35%) compared to the APs fractions. The PT and APTTS assays were used to measure the anticoagulant activity of the polysaccharide fractions. In general, the PT activity of the TPs and APs was not different from normal plasma values. The exception was the TPs treatment at 1000 mu g mL(-1) concentration. The APTTS test revealed that clotting time for both polysaccharides was prolonged regarding normal values at 1000 mu g mL(-1). Finally, the antitumor test in colorectal carcinoma (HTC-116) cell line, breast cancer (MCF-7) and human leukemia (HL-60) cell lines showed the cytotoxic effect of TPs and APs. Those results suggest the potential biotechnological application of sulfate galactan polysaccharides isolated from a Chilean marine resource.