Chapter 10 Oceania: Antidepressant Medicinal Plants Ian Edwin Cock and Matthew J. Cheesman Abstract Despite having the smallest land mass of the World Wildlife Fund (WWF)-declared ecozones, Oceania is amongst the most diverse fl oral regions of the world. Geographically, the region consists of Australia and New Guinea as the largest land masses, as well as the islands of Melanesia, Micronesia and Polynesia. Due to the island nature of the region, the fl ora has developed in isolation in various climatic conditions within the region, resulting in an extremely high degree of ende- mism. Furthermore, the harsh climatic conditions in some regions have resulted in a wealth of unique phytochemicals not found in plants from other regions globally. Coupled with possibly the world’s oldest continuous human inhabitation on the Australian mainland and a diversity of cultures in other Oceania regions, this has led to complex and sophisticated ethnopharmacological systems. Medicinal plants with unique properties have long been recognised by indigenous Oceania popula- tions, and this lore has been passed from generation to generation. Whilst often not well recorded, there is a wealth of knowledge of the medicinal value of the regions’ fl oral species for all types of therapeutic purposes. This chapter focuses on the plants of the region with known antidepressant uses and/or those plants which have phytochemistry consistent with antidepressant properties. This is by no means an exhaustive list, but instead serves to highlight some of the best known examples (e.g. kava-kava) and discuss examples of plants with established antidepressant mechanisms. For example, whilst we discuss the calmative properties of the Australian plant Backhousia citriodora , many other aromatic plants with similar essential oil components and thus similar therapeutic properties exist in the region and are not discussed here for the sake of brevity. Furthermore, despite the high degree of endemism of Oceania fl ora, several well-known species (e.g. Areca cat- echu L. and Nelumbo nucifera Gaertn.) have wide geographic ranges. Indeed, whilst I. E. Cock (*) Environmental Futures Research Institute , Griffi th University , Nathan Campus, 170 Kessels Road , Nathan , QLD 4111 , Australia School of Natural Sciences , Griffi th University , Nathan Campus, 170 Kessels Road , Nathan , QLD 4111 , Australia e-mail: i.cock@griffi th.edu.au M. J. Cheesman School of Biomedical Sciences , University of Queensland , St Lucia , QLD 4072 , Australia e-mail: [email protected] © Springer International Publishing Switzerland 2016 1 C. Grosso (ed.), Herbal Medicine in Depression, DOI 10.1007/978-3-319-14021-6_10 2 native to Oceania, A. catechu is better known as a component of the pharmacopoeias of other regions (e.g. India). However, these species also make an important contri- bution to Oceanic antidepressant medicinal plants and are therefore discussed in this chapter. Keywords Antidepressant • Australian plants • Melanesian plants • Micronesian plants • Polynesian plants • Complementary therapies 10.1 Geopolitical/Cultural Context Oceania is a large region generally regarded as stretching from the Straits of Malacca to the west coast of the Americas. It is described as all the lands of the Pacifi c Ocean and comprises four main regions: Australia, Melanesia, Micronesia and Polynesia (Fig. 10.1 ). The Australian continent accounts for the majority of the land mass, consisting of approximately 7,686,850 km 2 (86 % of the total Oceania land area). New Guinea (consisting of Papua, West Papua and Papua New Guinea) accounts for a further 10 % of the total land mass, with the remainder of the land spread between the remaining 27 nations. Australia also contributes the majority of the population (approximately 23,000,000 or 56 % of the total Oceania population). East Timor (1,143,667; 3 %), Hawaii (1,360,301; 3 %), Maluku Islands (1,895,000; 5 %), Micronesia Mariana Is. Hawaii Palan Caroline Is. Marshall Is. Kiribati New Salomon Is. Polynesia Guinea Melanesia Vanuatu Samoa Cook Is. Fiji New Caledonia Tonga Easter Island Australia New Zealand Fig. 10.1 The Oceania region, highlighting Australia, Melanesia, Micronesia and Polynesia 3 New Zealand (4,465,900; 11 %), Papua (8 %) and Papua New Guinea (5,172,033; 13 %) also have signifi cant populations, with lower populations in other regions (CIA World Fact Book 2015; United States Department of State 2015). The region is culturally diverse, with a wide variety of traditional cultural group- ings, as well as more recently arrived settlers. The region has some of the oldest continuous cultures in the world. Some studies estimate that the Australian Aborigines have lived continuously in Australia for as long as 80,000 years, making them possibly the oldest continuous culture in the world (Bowler et al. 2003). With such a long history, it is perhaps not surprising that the Aborigines developed a sophisticated and effective phyto-medical system and were able to treat most ill- nesses they encountered before European arrival (Cock 2011). At the other extreme, the Maori of New Zealand are a much more recent culture, arriving in New Zealand from other regions of Polynesia as recently as 700–800 years ago (McCormick 1939). Despite their recent history, the Maori people have also developed a plant- based medicinal system . It is also likely that they have brought traditional knowl- edge of similar plants with them when they arrived in New Zealand. The cultural diversity of the region also accounts for the varied usage patterns of some therapeutic plants. Piper methysticum G. Forst (kava-kava) is now recognised for its sedative properties and is used therapeutically internationally (Cock 2015). However, in various Melanesian and Polynesian cultures, the consumption of kava- kava is social or ceremonial and may be drunk at formal gatherings and as a welcoming for visitors to the village. Whilst these ceremonies may have originated from a traditional understanding of the therapeutic properties of this plant, they have developed signifi cance beyond medicinal for these cultures. Similarly, Australian Aborigine smoking ceremonies involving the burning of specifi c native plants to produce smoke were originally thought to be purely ceremonial. However, recent studies have demonstrated that the heating process may instead be required to create biologically active compounds (Sandgrove et al. 2014). Thus, whilst these practices took on a ceremonial aspect, it is possible that they originated from a tra- ditional understanding of the medicinal properties of the local fl ora. The Oceania region has diverse climatic and environmental conditions . The Australian continent ranges from arid/desert environments to tropical and subtropi- cal regions with high rainfall. There are also signifi cant temperate and equatorial regions. Much of Melanesia and Micronesia is also subtropical/tropical or equato- rial. Polynesia has wide environmental diversity, with much of the region also being subtropical/tropical or equatorial. Much of New Zealand and other southern regions of Polynesia have a temperate climate, with several alpine regions. Such climatic diversity has resulted in high fl oral biodiversity. In many regions with harsh cli- mates (e.g. the hot, arid inland regions of Australia), plant species have developed to survive in these environments, resulting in plants with unique secondary metabo- lite components. Furthermore, the isolation of the region from other regions has resulted in a high degree of endemism in fl oral species. Local traditional medicine systems have developed for both physical and psy- chological complaints . As with other regions worldwide, depression is a signifi cant medical issue in Oceania. Nowadays, much of the population relies on allopathic 4 pharmaceuticals for treatment. There has recently been a revival in interest in plant- based remedies. However, due to the lack of written records of some Oceania cultural groups and the greater knowledge of plant species from other regions, much of the plant-based treatments rely on the better known treatments from Europe and Asia (e.g. St John’s wort) (Cock 2015). Whilst usage of these remedies is relatively common in Oceania, they are exotic to the area and will not be considered in this chapter. A number of species that are either indigenous or endemic to Oceania are examined here. Some of those species (e.g. Piper methysticum ) have well estab- lished antidepressant uses. Other species have received less study and are included because either they have effects which are likely to be therapeutic in individuals suffering from depression or they contain phytochemical components with estab- lished antidepressant properties. 10.2 Search Methods Information was sourced using a variety of search engines including Google Scholar , PubMed and Scopu s. 10.3 References • Bowler JM, Johnston H, Olley JM, Prescott JR, Roberts RG, Shawcross W, Spooner NA. New ages for human occupation and climatic change at Lake Mungo, Australia. Nature 2003;421:837–40. • CIA World Fact Book, Oceania ( https://www.cia.gov/library/publications/ the- world- factbook/wfbExt/region_aus.html ). Accessed 10 Mar 2015. • Cock IE. The safe usage of herbal medicines: counterindications, cross- reactivity and toxicity. Pharmacognosy Commun. 2015;5(1):2–50. • Cock IE. Medicinal and aromatic plants—Australia. In: Ethnopharmacology, Encyclopedia of Life Support Systems (EOLSS). Developed under the auspices of UNESCO. Oxford, UK: EOLSS Publishers; 2011.