Potencial dos óleos essenciais de plantas no controle de insetos e microrganismos

Abstract

ResumoAs substâncias repelentes ou atraentes das plantas são, principalmente, de natureza terpênica e se apresentam como moléculas de baixo peso molecular e volátil. Essas substâncias, normalmente, são conhecidas como aromáticas e se denominam óleos essenciais, os quais se acumulam em todos os órgãos vegetais. Nos vegetais, os óleos essenciais desenvolvem funções relacionadas com sua volatilidade, agindo na atração de polinizadores, na proteção contra predadores, nos patógenos, na perda de água, no aumento de temperatura e também desempenhando funções ecológicas, especialmente como inibidoras de germinação. Essas características tornam as plantas que os produzem poderosas fontes de agentes biocidas, o que é largamente estudado nos agroecossistemas, principalmente no que concerne às ações bactericida, fungicida e inseticida. Os óleos essenciais têm como principais constituintes os monoterpenos, seguidos pelos sesquiterpenos, além de compostos aromáticos de baixo peso molecular. Sua função específi ca na planta ainda é desconhecida, porém se acredita que, durante o seu desenvolvimento, as plantas superiores sintetizam terpenóides essenciais para o próprio crescimento. Essas substâncias do metabolismo secundário podem agir como inibidores de germinação, proteção contra predadores, atração de polinizadores, entre outras. Entretanto, a avaliação desses compostos com fi nalidades diversas, como, por exemplo, no controle de microrganismos patogênicos de plantas cultivadas ou, ainda, como inseticida ou herbicida natural, é recente, visto que são poucos os trabalhos de pesquisa desenvolvidos e publicados nessa área. Esta revisão em artigo trata das interações dos óleos essenciais de plantas medicinais, silvestres e cultivadas com microrganismos e insetos.Palavras-chave: óleos essenciais, insetos, fungos, bactérias. AbstractThe repelling or attracting plants substances are mainly from terpenic nature and they appear as molecules with less molecular weight and volatile. Usually, these substances are known as aromatic or essential oils, which amass themselves at all herbal organs. In the herbs, essential oils develop functions related to volatility, acting to attract the pollinating, to protect against pathogens predators, in the missing of water, to rise the temperature and also making ecological functions, especially as a germination inhibitor. These features make the plants which produce these aromatics a powerful source of biocidal agents, being steadily studied in agroecosystems, principally because of the bactericidal, fungicidal, and insecticidal activities. The main components are the monoterpenes, followed by sesquiterpenes, besides aromatic compounds with low molecular weight. The specifi c function that essential oils turns out on the plant is still unknown; however, it is supposed that the higher plants synthesize terpenoids which are essential to their growth. These substances of secondary metabolism can act as germination inhibitors, protection against predators, pollinator attractors, among others. However, t...

Chemical identification of Tagetes minuta Linnaeus (Asteraceae) essential oil and its acaricidal effect on ticks

“…The results of Knaak and Fiuza (2010) showed that the production of essential oil is viable and profitable. However, to obtain high quality products that are competitive in the market, incentives are necessary to develop modern techniques of cultivation, selection and plant breeding.…”

“…For this reason, it is necessary to conduct insightful research on the chemical composition of plant-derived substances and their effects. The process of extracting solvents, the applications of the techniques in the field, conservation and plant selectivity also need to be further evaluated (KNAAK;FIUZA, 2010) Essential oils are distributed in a limited number of families, such as Asteraceae, and accumulate in all types of plant vegetative organs such as the flowers, leaves, barks, roots, rhizomes, fruits and seeds. In most cases, the biological function of the essential oil terpenoids remains obscure.…”

“…These attractive or repellent substances of plants are mainly terpenic in nature, of low molecular weight, and volatile. Such substances are usually referred to as aromatic essential oils, and they accumulate in all plant organs (KNAAK;FIUZA, 2010).…”

Chemical composition and insecticidal activity of Cymbopogon citratus essential oil from Cuba and Brazil against housefly

“…Although the mechanism of action of essential oils and its constituents is unknown, the appearance of toxic signs is fast (KNAAK & FIUZA, 2010). Any of these observations could explain the differences in development time and mortality of M. domestica treated with pure citral and citral found in the essential oil diluted in DMSO.…”

Antimicrobial, insecticidal, and antioxidant activity of essential oil and extracts of Guarea kunthiana A. Juss

“…The insecticidal action of essential oils can occur in different ways and may cause mortality, deformities at different stages of development, repellency, and deterrence. Through the contact, essential oils can interact with the tegument of insects, besides acting in digestive and neurological enzymes (Isman, 2006;Knaak and Fiuza, 2010).…”