Chemical composition of the essential oil of Psidium guajava leaves and its toxicity against Sclerotinia sclerotiorum

Globally, the fungus Sclerotinia sclerotiorum is considered as one of the most important phytopathogens, since it affects the production of several economically important crops. Further, it is difficult to control, thus increasing the use of pesticides. Therefore, the search for new substances, especially those extracted from plants, has received special attention to control this plant pathogen. The objective of the present study was to evaluate the yield and chemical composition of the essential oil extracted from the fresh leaves of guava collected during the rainy and dry seasons, and also to evaluate its toxicity against S. sclerotiorum. The experiment was a completely randomized design with five treatments and six replicates. The essential oil was extracted by hydrodistillation of the leaves and analyzed by gas chromatography-flame ionization detector and gas chromatography-mass spectrometry. The main compounds identified in the essential oil were trans-caryophyllene and ?-humulene. The essential oil at a concentration of 300 ?L exhibited 90% inhibition of the mycelial growth of S. sclerotiorum. This confirmed the antifungal potential of the essential oil of the guava leaves during both the sampling seasons

Efeito da secagem natural e artificial da biomassa foliar de psidium guajava sobre o teor e a composição química do óleo essencial

Psidium guajava L. is native to Central and South America. It is widely distributed and well adapted to Brazil, a producer of essential oils rich in terpenes. The objective of this study was to evaluate the effects of natural and artificial drying on the content and chemical composition of the essential oil of guava leaves (Psidium guajava L.) grown in Rio Verde (GO). The two treatments consisted of drying fresh leaves either naturally in the shade or artificially at 40°C. Chemical composition was analyzed qualitatively and quantitatively by gas coupled with mass spectrometer chromatography (GC/MS) and gas chromatography using a flame ionizer (GC-FID), respectively. The method of drying changed the content and chemical composition of the essential oil of guava leaves. Drying in the shade reduced the content and altered the constituents of the essential oil, whereas drying in an oven at 40°C, despite having reduced the amounts of the constituents, exhibited the highest essential oil content and increased the concentration of certain major constituents as compared to that in the natural shade drying method. The major components found in the essential oil of leaves regardless of the drying processes were trans-caryophyllene, ?-humulene, aromadendrene, ?-selinene, and selin-11-en-4?-ol. According to reports in the literature, these compounds possess fungicidal, insecticidal, antimicrobial, and anti-inflammatory activity, among others beneficial actions.Psidium guajava L. é uma planta nativa da América Central e do Sul, que está amplamente distribuída e bem adaptada no território brasileiro, produtora de óleo essencial rico em terpenos. O objetivo deste estudo foi avaliar o efeito da secagem natural e artificial sobre o teor e a composição química do óleo essencial das folhas de goiabeira (Psidium guajava L.), cultivada em Rio Verde (GO). Os tratamentos avaliados foram: folhas frescas; secagem natural à sombra e secagem em estufa a 40ºC. A composição química qualitativa e quantitativa foi analisada por cromatografia gasosa acoplada ao espectrômetro de massa (CG/MS) e cromatógrafo gasoso com ionizador de chama (CG-FID), respectivamente. O tipo de secagem alterou o teor e a constituição química do óleo essencial das folhas de goiabeira. A secagem a sombra reduziu o teor e a quantidade de constituintes do óleo essencial, enquanto a secagem em estufa a 40ºC apesar de ter reduzido a quantidade de constituintes, apresentou o maior teor de óleo essencial e aumentou a concentração de alguns constituintes majoritários em relação à secagem natural a sombra. Os componentes majoritários encontrados tanto no óleo essencial das folhas in natura quanto no óleo essencial obtido das folhas submetidas aos processos de secagem foram trans-cariofileno, ?-humuleno, aromadendreno, ?-selineno e o selin-11-en-4?-ol, e segundo relatos na literatura estes compostos possuem atividades fungicidas, inseticidas, antimicrobianas, anti-inflamatórias, entre outras

Harvest time on the content and chemical composition of essential oil from leaves of guava

The essential oil plants contents can be affected by several factors. For example, in certain plants, collection time has been observed to affect the content and chemical composition of the essential oil obtained from the plant. The objective of this study was to evaluate the effect of collection time on the content and chemical composition of the essential oil from guava ( Psidium guajava L.) leaves. Leaves were collected at different times of the day and the content and chemical composition of their essential oil was determined. Collection time did not qualitatively affect the chemical composition of the essential oil. However, concentration of certain substances in the oil, such as α-humulene and trans-caryophyllene, did significantly vary at different collection times. The main constituents of the essential oil of Psidium guajava are limonene (2.2-4.4%), trans-caryophyllene (18.1-17.1%), α-humulene (26.3-20.4%), aromadendrene (7.6-12.2%), α-selinene (7.3-11.3%), caryophyllene oxide (3.7-3.3%), humulene epoxide II (4.1-1.9%), and selin-11-en-4α-ol (7.2-11.1%). Leaves collected at 7:00 AM had higher essential oil production, with a content of 0.38% (d.b.), whereas leaves collected at 7:00 PM had lower essential oil production, 0.24% (d.b.). Chemical analysis showed that sesquiterpene compounds represented the highest concentration (62.0%), and monoterpenoids and monoterpenes represented the lowest concentrations (1.1 and 2.2%, respectively). Chemical classes that underwent major changes with respect to collection time were monoterpenes, sesquiterpenes, and sesquiterpenoids (2.2-4.4%, 63.8-61.7%, and 15.9-13.2%, respectively).Existem fatores que podem afetar o conteúdo de óleo essencial das plantas, sendo o horário de coleta um deles. Assim, observa-se que o teor e a composição química de óleo essencial podem variar em certas plantas de acordo com horário de coleta. O objetivo deste trabalho foi avaliar o efeito do horário de coleta sobre o conteúdo e a composição química do óleo essencial das folhas de goiabeira ( Psidium guajava ). Folhas de Psidium guajava foram coletadas em diferentes horários do dia para determinar teor e composição química de seu óleo essencial. O óleo essencial não apresentou variação qualitativa da composição química em relação ao horário de coleta das folhas de Psidium guajava , mas alterou a concentração das substâncias, entre elas o α-humuleno e o trans-cariofileno. Os constituintes principais do óleo essencial das folhas de Psidium guajava são o limoneno (2,2-4,4%), trans-cariofileno (18,1-17,1%), α-humuleno (26,3-20,4%), aromadendreno (7,6-12,2%), α-selineno (7,3-11,3%), óxido de cariofileno (3,7-3,3%) epóxido de humuleno II (4,1-1,9%) e o selin-11-en-4α-ol (7,2-11,1%). No entanto, a maior produção de óleo essencial, foi obtida com as folhas coletadas às 19h, apresentando conteúdo de 0,38% (b.s.) e a mais baixa produção às 07h, apresentando conteúdo de 0,24% (b.s.). Através da análise química, identificou-se que compostos sesquiterpênicos apresentaram uma maior concentração (62,0%) e os monoterpenos e monoterpenoides foram os que apresentaram menor concentração (2,2 e 1,1%, respectivamente). As classes que sofreram maiores mudanças em relação ao horário de coleta foram os monoterpenos (2,2-4,4%) e os sesquiterpenos e os sesquiterpenoides (63,8-61,7% e 15,9-13,2%, respectivamente)

Harvest time on the content and chemical composition of essential oil from leaves of guava

ABSTRACT: The essential oil plants contents can be affected by several factors. For example, in certain plants, collection time has been observed to affect the content and chemical composition of the essential oil obtained from the plant. The objective of this study was to evaluate the effect of collection time on the content and chemical composition of the essential oil from guava ( Psidium guajava L.) leaves. Leaves were collected at different times of the day and the content and chemical composition of their essential oil was determined. Collection time did not qualitatively affect the chemical composition of the essential oil. However, concentration of certain substances in the oil, such as α-humulene and trans-caryophyllene, did significantly vary at different collection times. The main constituents of the essential oil of Psidium guajava are limonene (2.2-4.4%), trans-caryophyllene (18.1-17.1%), α-humulene (26.3-20.4%), aromadendrene (7.6-12.2%), α-selinene (7.3-11.3%), caryophyllene oxide (3.7-3.3%), humulene epoxide II (4.1-1.9%), and selin-11-en-4α-ol (7.2-11.1%). Leaves collected at 7:00 AM had higher essential oil production, with a content of 0.38% (d.b.), whereas leaves collected at 7:00 PM had lower essential oil production, 0.24% (d.b.). Chemical analysis showed that sesquiterpene compounds represented the highest concentration (62.0%), and monoterpenoids and monoterpenes represented the lowest concentrations (1.1 and 2.2%, respectively). Chemical classes that underwent major changes with respect to collection time were monoterpenes, sesquiterpenes, and sesquiterpenoids (2.2-4.4%, 63.8-61.7%, and 15.9-13.2%, respectively)