Alejandro Urzúa

Total antioxidant potential of resinous exudates from Heliotropium species, and a comparison of the ABTS and DPPH methods

Total reactive antioxidant potential (TRAP) of resinous exudates from Heliotropium species was evaluated by measuring the bleaching of stable free radicals. The antioxidant capacity of the resinous exudates in Trolox equivalents, evaluated from the bleaching of ABTS derived radical cations, ranged from 2.0 M (H. huascoense) to 5.2 M (H. stenophyllum), indicating a very high concentration of phenolic compounds. Considerably smaller values were obtained by measuring the bleaching of DPPH radicals. The ratio between the values obtained employing ABTS derived radicals and DPPH, ranged from 37 (H. megalanthum) to 4.5 (H. chenopodiaceum variety typica). The magnitude of the difference can be considered as an indication of the relative reactivity of the antioxidants present in the exudates. Similar ratios were observed when stoichiometric coefficients were evaluated for representative purified flavonoids obtained from the resinous exudates.

Antimicrobial study of the resinous exudates and of diterpenoids and flavonoids isolated from some Chilean Pseudognaphalium (Asteraceae).

The antimicrobial properties of the resinous exudates from twigs and leaves of four Chilean species of Pseudognaphalium: P. viravira, P. robustum, P. heterotrichium and P. cheiranthifolium were tested against six gram negative bacteria and five gram positive bacteria. The extracts share similar antimicrobial activities against the gram positive bacteria. The antimicrobial activity correlated very well with the presence in the resinous exudates of ent-16-kauren-19-oic acid and to a lesser extent with the presence of ent-9(11),16-kauradien-19-oic. Introduction of an hydrophilic 3 beta-OH drastically reduced the antimicrobial activity of these compound. The activity was not correlated with the flavonoid content of those resinous exudates.

Efficacy of Essential Oils from Edible Plants as Insecticides Against the House Fly, Musca Domestica L.

The compositions of 12 essential oils (EOs) obtained by hydrodistillation of edible fruits and herbs were analyzed by gas chromatography/mass spectroscopy (GC/MS). The insecticidal activity of each oil against the house fly Musca domestica was evaluated by placing flies in a glass jar with a screw cap that held a piece of EO-treated cotton yarn. The dose necessary to kill 50% of flies (LC50) in 30 min was determined at 26 ± 1°C. Twelve EOs and 17 individual terpenes were assayed against M. domestica, showing LC50 values ranging from 3.9 to 85.2 and from 3.3 to >100 mg/dm3, respectively. EO from Citrus sinensis was the most potent insecticide (LC50 = 3.9 mg/dm3), followed by EOs from C. aurantium (LC50 = 4.8 mg/dm3) and Eucalyptus cinerea (LC50 = 5.5 mg/dm3). According to GC/MS analysis, limonene (92.47%), linalool (1.43%), and β-myrcene (0.88%) were the principal components of C. sinensis EO. Limonene was also the principal constituent (94.07%) of C. aurantium, while 1,8-cineole (56.86%) was the major constituent of E. cinerea EO. 1,8-Cineole was most active against M. domestica (LC50 = 3.3 mg/dm3), while (4R)(+)-limonene, was moderately active (LC50 = 6.2 mg/dm3). Dimethyl 2,2-dichlorovinyl phosphate (DDVP) selected as a positive control, showed an LC50 of 0.5 mg/dm3. EOs from C. sinensis, C. aurantium, and E. cinerea show promise as natural insecticides against houseflies.

A Structure-Activity Study of Antibacterial Diterpenoids

An analysis of the antibacterial activities of 15 terpenoids, eleven of which were previously described by us and four were extracted from the literature, suggested two structural requirements for activity of these and related compounds: a hydrophobic moiety, consisting of a substituted decalin skeleton, and a hydrophilic region possessing one hydrogen-bond-donor group. These structural requirements are responsible for an optimal insertion of these and related compounds into cell membranes, as suggested by the results of docking some of these compounds into a model phospholipid bilayer.

Antimicrobial study of the resinous exudate and of diterpenoids isolated from Eupatorium salvia (Asteraceae).

The antimicrobial properties of the resinous exudate from twigs and leaves of Eupatorium salvia were tested against five gram-negative and five gram-positive bacteria. Comparison of the antimicrobial activities of 7-hydroxy-8(17)-labden-15-oic acid (salvic acid) and of its acetate, both compounds isolated from the plant, with that of the crude extract suggested that the latter ester derivative was the major active component in the exudate. These results validate the vernacular medicinal use of Eupatorium salvia as an antiseptic agent.

2,5-diaryl-3,4-dimethyltetrahydrofuranoid lignans

Abstract Aristolochia chilensis has yielded the new 2,5-diaryl-3,4-dimethyltetrahydrofuranoid lignans (+)-aristolignin and (−)-zuonin-A. These and related tetrahydrofuranoids have been classified into six stereochemical groups.

Filifolinol, a rearranged geranyl aromatic derivative from the resinous exudate of Heliotropium filifolium

Abstract The resinous exudate of Heliotropium filifolium has yielded a new rearranged geranyl aromatic derivative. This result is in agreement with the botanical affinity of some members of the Cochranea section of Heliotropium .

Antibacterial Properties of 3 H-Spiro[1-benzofuran-2,1’-cyclohexane] Derivatives from Heliotropium filifolium

A re-examination of cuticular components of Heliotropium filifolium allowed the isolation of four new compounds: 3’-hydroxy-2’,2’,6’-trimethyl-3H-spiro[1-benzo-furan-2,1’-cyclohexane]-5-carboxylic acid (2), methyl 3’-acetyloxy-2’,2’,6’-trimethyl-3H-spiro[1-benzofuran-2,1’-cyclohexane]-5-carboxylate (3), methyl 3’-isopentanoyloxy-2’,2’,6’-trimethyl-3H-spiro[1-benzofuran-2,1’-cyclohexane]-5-carboxylate (4) and methyl 3’-benzoyloxy-2’,2’,6’-trimethyl-3H-spiro[1-benzofuran-2,1’-cyclohexane]-5-carboxylate (5). Compounds 2-5 were identified by their spectroscopic analogies with filifolinol (1), and their structures confirmed by chemical correlation with 1. The antimicrobial properties of the compounds were tested against Gram positive and Gram negative bacteria. Some of them proved to be active against Gram positive, but inactive against Gram negative bacteria. In searching for structure-activity relationships from the obtained MIC values, lipophilicity was shown to be an important variable.

Fate of Ingested Aristolochic Acids in Battus archidamas

Key Word Index--Battus archidamas; Papilionidae; Lepidoptera; aristolochic acids; sequestration; excretion; metabolism. Abstract--Battus archidamas larvae reared on Aristolochia chilensis sequester aristolochic acids selectively and independently of lipophilicity. A considerable proportion of the ingested acids can be recovered from the excreta, but the amounts which remain unaccounted for suggest that metabolic detoxification is the principal mean of disposing of these substances by the insects.

INSECTICIDE PROPERTIES OF THE ESSENTIAL OILS FROM HAPLOPAPPUS FOLIOSUS AND BAHIA AMBROSOIDES AGAINST THE HOUSE FLY, MUSCA DOMESTICA L

The compositions of the essential oils (EO’s) obtained by hydro distillation from fresh leaves of haplopappus foliosus and bahia ambrosoides was analyzed by gas chromatography/mass spectroscopy (GC/MS). The insecticidal activity of each oil against the house fly Musca domestica was evaluated by placing flies in a glass jar with a screw cap that held a piece of EO-treated cotton yarn. The dose necessary to kill 50% of flies (LC 50 ) in 1 h was determined at 26±1°C. The essential oil from haplopappus foliosus was the most potent insecticide (LC 50 = 4.43 mg/dm 3), wile the EO from bahia ambrosoides shows only moderated insecticide activity (LC 50 = 19.27 mg/dm3). According to GC and GC/MS analysis, limonene (28,00%); epi-bicyclosesquiphellandrene (9,84%); bornyl acetate (7,74%); 4-terpineol (6,36%); p-cymene (6,00%); agarospirol (5,53%); α-muurolene (4,34%); δ-cadinene (3,98%) and caryophyllene (3,97%) were the principal components of haplopappus foliosus EO and limonene (28,16%); α-pinene (11,12%); germacrene D (8,81%); sabinene (5,93%); α-thujene (3,48%); γ-curcumene (3,45%) y α-bergamotene (3,36%) were the principal components of bahia ambrosoides EO. The EO from haplopappus foliosus seem promising as a natural insecticide against houseflies and the difference with the activity of the EO of bahia ambrosoides can be ascribed to the content of oxygenated monoterpenoids and sesquiterpenoids.