The Production of Benzoin: Comparison
Please note this is a comparison between Version 1 by Yangyang Liu and Version 3 by Conner Chen.

Benzoin is a pathologic exudation produced by plants of the family Styrax. It is secreted by traumatic resin ducts after injury, which are derived from parenchymal cells in secondary xylem by schizolysigeny. Some 63 chemical constituents have been isolated and identified from this resin, including balsamic acid esters, lignans and terpenoids. It has a long history of applications, including as incense along with olibanum, a flavor enhancer in the food industry, materials in the daily chemistry industry as well as therapeutic uses. 

  • benzoin
  • production
  • phytochemistry

1. Introduction

Plant resin is defined primarily as a lipid-soluble mixture of volatile and nonvolatile terpenoids and/or phenolic secondary compounds. There are two kinds of resins: terpenoid resin and phenolic resin [1]. Benzoin, a representative of phenolic resins, is revealed that mainly contains benzoic acid, cinnamic acid and their derivatives in primary volatile compounds and triterpenoids and lignans in dominant nonvolatile compounds. Several works have stated that crude extractions of benzoin or purified monomers obtained from benzoin exhibit pharmacological activities, such as antitumor, neuroprotective, cytotoxic, antimicrobial, anti-inflammatory and pesticidal properties [2][3][4][5][6][2,3,4,5,6]. Furthermore, benzoin can be used as a fragrance in religious rituals along with olibanum; as an industrial material for perfume, detergent and other daily chemicals owing to its distinctive fixation; and as a natural flavoring and natural adjuvant due to its olfactory and preservative features [7].
As members of a group who are interested in exploring the quality differences among a variety of types of commercial benzoin and evaluating techniques for quality assessment. One proposes coniferyl benzoate as a Q-marker (chemicals which can reflect the quality of this Chinese herb) of benzoin due to its prominent bioactivity. However, the process of benzoin’s production has not been reported, which may have an impact on its quality and efficacy. Meanwhile, these reviews summarized compounds identified by GC-MS or isolated from tree bark.

2. Benzoin-Producing Plants

2.1. Benzoin-Producing Plants

In order to find out the origin of benzoin, we should understand what benzoin is. It belongs to Styrax, the largest genus in the Styracaceae family. Styrax is renowned for its resinous material production, which makes it predominant in the family. Benzoin has plentiful names. In Germany, it is called benzoebaum. In Spain, it is bálsamo de Benjuí [8][9]. It is also categorized into balsam with storax, Tolu balsam and Peru balsam [9][10]. Some literatures recognize benzoin as benzoin gum, which is confused with the concepts of gum and resin. Gum is a water-soluble chain of polysaccharides [1]. Moreover, two major benzoins universally exist in commercial markets: Siam benzoin and Sumatra benzoin. Although the categorization varies in different places, it is widely shared that Siam benzoin is produced by plants belonging to S. tonkinensis (Pierre) Craib ex Hartwiss, while Sumatra benzoin is excreted by trees of S. benzoin Dryand and S. perelleloneurum Perkins. Some think that Siam benzoin can provide a sweeter and vanilla-like odor, which makes Siam benzoin superior to Sumatra benzoin in the food industry, regardless of prices. In contrast, the Sumatran type is spicier and features a styrax-like odor, playing a role in the daily chemical industry and pharmaceutical preparations [10][11][12][11,12,13]. There are also other benzoin resins produced by Styrax, with benzoin in lesser field and quality, such as Bolivia benzoin produced by S. pearceivar bolivianum, Bogota Storaque by S. Aureum and Solid Storaque by S. officinale [13][14].
Storax and styrax are easily confused, and both have predominant phenolic components and similar olfactory properties. Also, the use of “styrax” to refer to these two resins in the literature worsens this situation. However, the resin produced from the Styrax species (Styracaceae) is styrax, while (Altingiaceae) storax is from the Liquidambar species [9][10].

3. Benzoin-Producing Process

2.2. Benzoin-Producing Process

There are a few reports regarding the resin secretory structures of benzoin. Deng et al. revealed that traumatic resin ducts in Styrax are formed by parenchymal cells in secondary xylem by schizolysigeny after injury [14][15]. The resin is not secreted to the outside of plants until injury take place [1]. Furthermore, continuous injuries could promote the regeneration of new resin ducts [15][16]. They also discovered that ethephon, a plant growth regulator, can remarkably boost the yield of benzoin by increasing the dimension and number of traumatic resin ducts to promote their distribution [14][15]. However, the compartmentation sequestration process of benzoin resin has been less researched.
The trees belonging to Styrax have no ability to secrete resin unless their stems get injured. Consequently, benzoin resin is regarded as a pathologic exudation of plants in a stress response to external injuries [16][17]. Pinyopusarerk described the tapping of benzoin in Laos [17][18]. The method involves tapping several staggered rectangle notches in the plant’s cambium between 30 centimeters from the ground and the height of the first branches and loosening the bark of the notches’ lower part to induce the formation of benzoin resin. In Malaysia, these notches are inverted triangles, and there are three notches at the same level. In Indonesia, trapezoid-shaped cuts and V-shaped cuts are tapped by wedges between the bark and wood to create incisions and collect benzoin [7]. However, there is no information on the relationship between the size of notch and secretion of benzoin. It should be noted that in dry conditions, the tapped incisions should be cleaned up to ensure the mobility of the resin. However, incisions will be closed by bark to prevent resin exudation in wet years [17][18].
Several weeks after being tapped, the incisions will be covered with benzoin in the form of tears. At first, quite a lot of transparent, soft and viscous gum or oil along with water exudes and flows around the wound. Then, that exudation, exposed to the air, will evaporate and condense into considerably sizable pieces, and become hard, and eventually fragile resin forms. In that process, evaporation of volatile components, oxidation and polymerization take place. The chemical composition of the resin becomes more complex, and the pale fresh benzoin darkens, so that it exhibits similar features and characteristics to benzoin. It is shown that trees with dark, thick and rough bark can produce more benzoin. Also, a tree in a larger diameter class produces more benzoin [7][18][7,19].
Farmers can collect benzoin several times from one tree. The first resin flow is called takasan, with white inner resin and yellowish resin. The second resin flow is lecet, whose color ranges from white to dark brown. The third resin flow is named tahir or juror. Differing from frankincense, with which more valuable resins occur in its second or third woundings, the first flow of benzoin resin has fewer impurities and dries more easily [7].
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