Xylosma G. Forst. Genus: Comparison
Please note this is a comparison between Version 2 by Rodrigo Duarte-Casar and Version 1 by Rodrigo Duarte-Casar.

TXylosma G. Forst. is a genus of plants belonging to the Salicaceae Mirb. family, to which the Xylosma genu with intertropical dis tribelongs, is famously medicinal because of the Salix gution in America, Asia, and Oceania. Of the 100 acceptenud s (willow), the pharmacological properties of which were already used in ancient Mesopotamia, andpecies, 22 are under some level of conservation risk. In this review, around 13 species of the genus used as medicinal plants were extolled in the first century CE, in Dioscorides’ De Materia Medicafound, mainly in Central and South America, with a variety of uses, among which antimicrobial is the most common.

  • Xylosma
  • ethnopharmacology
  • phytochemicals
  • Salicaceae

1. Genus

The Salicaceae Mirb. family, to which the Xylosma genus belongs, is famously medicinal because of the Salix genus (willow), the pharmacological properties of which were already used in ancient Mesopotamia, and were extolled in the first century CE, in Dioscorides’ De Materia Medica [8,9].
The Xylosma genus is one of the 55 that conform the Salicaceae family [9], and is composed of 100 accepted species [10], although others list 45 [11]. Until recently, it was included in the now-deprecated Flacourtiaceae family, but has now been assigned to Salicaceae [12]. The name stems from the Greek words for “wood” and “smell” in reference to odoriferous quality of the wood of some Pacific species of the genus [11], presumably X. orbiculata and X. suaveolens used to perfume coconut oil by early South Pacific inhabitants [13]. At first, the genus was named Myroxylon (myrrh-wood) but was changed to Xylosma to avoid confusion with South American balsam trees [14]. Not all species in the genus are sweet-smelling: X. maidenii timber, for example, is foul-smelling. Xylosma species are described in detail by Woodson et al. [15].
In shrubs or small trees, often with axillary spines, the branchlets commonly lenticellate. Leaves alternate, sometimes borne in fascicles, usually short-petiolate, estipulate, the blade is often ±coriaceous, usually glandular-dentate, penninerved, rarely entire-margined, without pellucid-glands. Inflorescences axillary, fasciculate or contracted-racemose, and are rarely racemose. Flowers are small, dioecious, or rarely polygamous; pedicels are articulated above the base, and the bracts are minute; sepals 4-5(-6), imbricate, usually scale-like, slightly connate at the base, often ciliolate along the margins, usually persistent; petals none; stamens ∞ (8–35 in Panamanian spp.), usually surrounded by an annular or glandular, fleshy disc, the filaments free, filiform, short- to usually long-exserted, the anthers minute, basifixed, extrose, longitudinally dehiscent; ovary sessile, inserted on an annular disc, 1-locular, with 2–3, rarely 4–6, parietal placentas, each placenta with 2, sometimes 4–6, ovules, the style entire or ±divided, sometimes very short, the stigmas scarcely dilated to dilated; rudimentary ovary wanting in male flowers. Fruits baccate, rather dry, indehiscent, surmounted by the persistent style, the pericarp rather thin-coriaceous, the seeds 2–8, +angular by mutual pressure, the testa thin; endosperm copious; embryo large, the cotyledons broad.
Species in the Xylosma genus have several uses and properties, from landscaping (Xylosma congesta (Lour.) Merr.), beekeeping (Xylosma venosa N. E. Br. [16]), timber, firewood, to food and medicine; notably Xylosma longifolia Clos. Due to the thorns that some species of the genus have, common names such as “do not touch me” (Xylosma coriacea (Poit.) Eichler) or “deer antlers” (Xylosma spiculifera (Tul.) Triana and Planch.) are used for them [17]. Eleven species of the genus, particularly Xylosma vincentii Guillaumin, are known to be nickel hyperaccumulators [18,19] which presents potential for phytoremediation and phytomining [20].

2. Distribution and Localization

Species belonging to the Xylosma genus are present in subtropical America, Southeast Asia, and Oceania. Of the 100 species listed in the genus [10], 61 are found in America, 8 in Asia, and 31 in Oceania. Figure 1 shows examples of species of the genus. The map in Figure 2 shows the intertropical, and to a lesser extent, temperate, distribution of Xylosma species, by country.
Figure 1. Xylosma flexuosa (Kunth) Hemsl. leaves and berries, left. Xylosma congesta (Lour.) Merr. inflorescence, right. Image sources: left, Public Domain (CC0); right, Miwasatosi, GDFL license.
Figure 2. Worldwide Xylosma distribution, by country, after [10].
Of the 100 species of the genus, 7 are listed as vulnerable, 9 as endangered, and 6 as critically endangered. In total, 22% of the species in the genus are considered as species of concern [21]. This should be considered when evaluating potential industrial uses for these species.

3. Ethnopharmacological and Ethnoveterinary Usage

Of the 100 species of the genus, few appear in the scientific literature, and even fewer are mentioned from an ethnopharmacological or ethnoveterinary perspective. Notwithstanding, Xylosma species are a part of the traditional Chinese medicinal system, with documented uses of X. congesta appearing as early as the XVI century CE [25]. Few of the Xylosma species are recognized as medicinal. Table 1 summarizes the species with reported medicinal use along with their stated ethnopharmacological uses, when available. The Anatomical Therapeutic Chemical (ATC) Classification by the World Health Organization (WHO) is used to classify the uses for each species [26]. Not all species are identified in the literature, with general mentions as “Xylosma sp.” in some cases.
Table 1. Medicinal and veterinary use of Xylosma species, listed in alphabetical order.

In Vitro Activity

In vitro research on biological activity of Xylosma species centers around 7 identified species and one unspecified one. The research figures are summarized in Figure 5, and the research is detailed in Table 2.
Figure 5. Summary of in vitro activity of Xylosma species.
Table 2. In vitro activity of Xylosma extracts. Species are in alphabetical order.