Today, there is increasing interest in discovering new bioactive compounds derived from ethnomedicine. Preparations of guava (Psidium guajava L.) leaves have traditionally been used to manage several diseases. The pharmacological research in vitro as well as in vivo has been widely used to demonstrate the potential of the extracts from the leaves for the co-treatment of different ailments with high prevalence worldwide, upholding the traditional medicine in cases such as diabetes mellitus, cardiovascular diseases, cancer, and parasitic infections. Moreover, the biological activity has been attributed to the bioactive composition of the leaves, to some specific phytochemical subclasses, or even to individual compounds. Phenolic compounds in guava leaves have been credited with regulating blood-glucose levels. Thus, the aim of the present review was to compile results from in vitro and in vivo studies carried out with guava leaves over the last decade, relating the effects to their clinical applications in order to focus further research for finding individual bioactive compounds. Some food applications (guava tea and supplementary feed for aquaculture) and some clinical, in vitro, and in vivo outcomes are also included.

Health Effects of Psidium guajava L. Leaves: An Overview of the Last Decade

Knowledge of medicinal plants is not only one of the main components in the structure of knowledge in local medical systems but also one of the most studied resources. This study uses a systematic review and meta-analysis of a compilation of ethnobiological studies with a medicinal plant component and the variable of gender to evaluate whether there is a gender-based pattern in medicinal plant knowledge on different scales (national, continental, and global). In this study, three types of meta-analysis are conducted on different scales. We detect no significant differences on the global level; women and men have the same rich knowledge. On the national and continental levels, significant differences are observed in both directions (significant for men and for women), and a lack of significant differences in the knowledge of the genders is also observed. This finding demonstrates that there is no gender-based pattern for knowledge on different scales.

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Effect of Gender on the Knowledge of Medicinal Plants: Systematic Review and Meta-Analysis

Ethnobiology has been defi ned classically as the study of the interactions of people and the environment. It is in fact a complex fi eld of knowledge and action that interfaces with many scientifi c disciplines. These interfaces result in different approaches and theoretical challenges. Ethnobiology occupies a privileged position because of its potential to integrate local and global knowledge, to connect cultures and academic approaches, and to relate biological and social aspects of the human experience to the environment. The term “ ethnobiology” refers to a union of competences that encompass aspects ranging from cultural to biological, comprising the study of very diverse relationships. It is challenging to defi ne such a complex fi eld, which involves different approaches and theoretical problems. Classically, ethnobiology has been defi ned as the study of the interactions of people and the environment. This sometimes makes it appear that the term is associated with human ecology and ethnoecology 1 . Darrell Posey ( 1987a ), one of the greats of ethnobiology, sees it as the study of knowledge and concepts developed by any culture on biology. 1 In this regard, for further debate, see Begossi ( 1993 , 2004 ) and Alves and Souto ( 2010 ). In another chapter of this book, we introduce a discussion on the relationships between ethnobiology and ethnoecology. This chapter is a revised and updated version of the “Introduction” published in the book Ethnobiology and Biodiversity (Albuquerque 2005 ). U. P. Albuquerque (*) Laboratory of Applied and Theoretical Ethnobiology, Department of Biology , Federal Rural University of Pernambuco , Rua Dom Manoel de Medeiros s/n, Dois Irmãos , 52171-900 Recife , Pernambuco , Brazil e-mail: upa677@hotmail.com A. G. C. Alves Department of Biology , Federal Rural University of Pernambuco , Rua Dom Manoel de Medeiros s/n, Dois Irmãos , 52171-900 Recife , Pernambuco , Brazil e-mail: agcalves.ufrpe@gmail.com

Introduction to Ethnobiology

Antioxidant and antibacterial properties of guava leaf extracts as affected by solvents used for prior dechlorophyllization

The alarming growth of the number of antibiotic resistant bacteria and difficulties in treatment of infections have initiated a search for new antibacterial compounds and develop new alternative strategies in combating bacterial infections. Plant-derived compounds could exhibit a direct antibacterial activity and/or an indirect activity as antibiotic resistance modifying compounds, which, combined with antibiotics, increase their effectiveness. This ability of plant active substances reflects in modification or blocking of resistance mechanism so that bacterium becomes sensitive to antibiotic or the antibiotic acts when in lower concentrations. The systematic screening of plant-derived bioactive compounds, including those which can synergistically act with antibiotics, as resistance modifying agents represents a potential approach to overcome bacterial resistance. Therefore, the goals of this chapter are (i) an update of literature review on synergism between plant extracts and antibiotics, (ii) presentation of experimental results of synergistic activity of selected plant extracts and antibiotics and (iii) concluding remarks.

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Synergistic Activity of Antibiotics and Bioactive Plant Extracts: A Study Against Gram-Positive and Gram-Negative Bacteria

Ethnopharmacological and ethnobotanical approaches are described in the literature as efficient to identify plants of interest for phytochemical and pharmacological studies. In the present work, we reflect on the quality of the data collected in ethno-directed studies. In accordance to the problems identified in published studies, and their theoretical and methodological underpinnings, we believe that these studies are poorly suited to contribute to the advancement of research aimed at the development of novel drugs.

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Are ethnopharmacological surveys useful for the discovery and development of drugs from medicinal plants

Psidium guajava L. and Psidium brownianum Mart ex DC. potentiate the effect of antibiotics against Gram-positive and Gram-negative bacteria

Studies have reported that gender influences the variation of knowledge of local medical systems. However, most of the ethnobiological studies that analyze the variation of knowledge have focused on analyzing only the richness of known resources. Therefore, in this review we discuss the importance of analyzing the variation of knowledge between genders with a multifactorial and non-unidirectional perspective. It also presents proposals for future studies that analyze the influence of gender on local medical systems, considering the dynamics of social-ecological systems.

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Wendy Marisol Torres Avilez

Papers

Are ethnopharmacological surveys useful for the discovery and development of drugs from medicinal plants

Psidium guajava L. and Psidium brownianum Mart ex DC. potentiate the effect of antibiotics against Gram-positive and Gram-negative bacteria

Dynamics of social-ecological systems: gender influence in local medical systems