Acylsugars are a group of plant-derived protective

secondary metabolites Secondary metabolites, also called specialised metabolites, toxins, secondary products, or natural products, are organic compounds produced by any lifeform, e.g. bacteria, fungi, animals, or plants, which are not directly involved in the nor ...

that lack

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seve ...

. They typically consist of

aliphatic In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated, like hexane, ...

acyl In chemistry, an acyl group is a moiety derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids. It contains a double-bonded oxygen atom and an alkyl group (). In organic chemistry, the acyl group ( I ...

groups of low to medium

chain A chain is a wikt:series#Noun, serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression (physics), compression but line (g ...

lengths

esterified In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides are ...

to the

hydroxyl group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

s of

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, usi ...

sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refi ...

. Presence of such acyl groups gives these compounds

hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, ...

properties. This group of compounds has been extensively studied in

tomato The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word , ...

and related species, in which these compounds are produced and secreted in sporadic amounts from

trichomes Trichomes (); ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a pla ...

on the plant leaf and

stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other structure * Stipe (mycology), the stem of a mushr ...

surface. Production of copious quantities of these acylsugars give a sticky feel to the plant tissue. In particular, this flower has shown to distract herbivorous insect pests against thrips damage. It is believed that acylsugars provide physical and/or

chemical defense Chemical defense is a life history strategy employed by many organisms to avoid consumption by producing toxic or repellent metabolites or chemical warnings which incite defensive behavioral changes. The production of defensive chemicals occurs in ...

to the

plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...

. Acylsugars are nonvolatile and

viscous The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...

polyesters Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natura ...

that consist of acyl chains on

backbones. These attached acid chains may vary in length from short to medium which affects the phenotypic characteristics of the

. Other factors that may affect plant

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological prop ...

includes the presence of either

, the number of acyl chains as well as the total amounts of acyl sugars.

Distribution

Acylsugars are produced in the secretory glandular

of various plants, specifically those that belong to the family

Solanaceae The Solanaceae , or nightshades, are a family of flowering plants that ranges from annual and perennial herbs to vines, lianas, epiphytes, shrubs, and trees, and includes a number of agricultural crops, medicinal plants, spices, weeds, and o ...

. These compounds are identified to be responsible for physical and/or

plant defense. Additionally, potential commercial applications were also found in these compounds. Some species that are known to produce acylsugars include ''

Solanum lycopersicum The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish wor ...

'', '' Solanum pennellii'', ''

Solanum habrochaites ''Solanum habrochaites'' (syn. ''Lycopersicon hirsutum''), the hairy tomato, is a species of flowering plant in the family Solanaceae The Solanaceae , or nightshades, are a family of flowering plants that ranges from annual and perennial he ...

'', ''

Nicotiana benthamiana ''Nicotiana benthamiana'', colloquially known as benth or benthi, is a species of ''Nicotiana'' indigenous to Australia. It is a close relative of tobacco. A synonym for this species is ''Nicotiana suaveolens'' var. ''cordifolia'', a descrip ...

'', '' Petunia axillaris'' and ''

Petunia integrifolia ''Petunia integrifolia'' (syn. ''Petunia violacea''), the violet petunia or violetflower petunia, is a species of wild petunia with violet-colored blooms. ''Petunia integrifolia'' is native to Argentina. ''P. integrifolia'' bears flowers approxim ...

''.

Functions

The function of acylsugars has been the subject of much research. For instance, acylsugars in ''

Solanum ''Solanum'' is a large and diverse genus of flowering plants, which include three food crops of high economic importance: the potato, the tomato and the eggplant (aubergine, brinjal). It is the largest genus in the nightshade family Solanacea ...

pennellii'' discourage pests from laying eggs and contain compounds that are toxic to

herbivores A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

. A study showed that this natural insect-repellent property may lead to the breeding and development of a

thrips Thrips (order Thysanoptera) are minute (mostly long or less), slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on plants by puncturing and sucking up the contents, although a few are ...

-resistant tomato which could be of commercial benefit. Additionally, acylsugars from other

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial ...

were also found to give protection against

and plant

pathogens In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a ger ...

.{{cite journal , last1=Kim , first1= K. K. , last2=Ji , first2=W. M. , last3=McKnight , first3=T. , date=April 2018 , title=Candidate gene network for acylsugar metabolism and plant defense in wild tomato Solanum pennellii , url=https://www.biorxiv.org/content/10.1101/294306v1 , journal=Plant Physiology , volume=160 , issue=2012 , pages=1854–1870 , doi=10.1104/pp.112.204735 , pmc=3510116 , pmid=23054567 Acylsugars are also classified as

amphiphile An amphiphile (from the Greek αμφις amphis, both, and φιλíα philia, love, friendship), or amphipath, is a chemical compound possessing both hydrophilic (''water-loving'', polar) and lipophilic (''fat-loving'') properties. Such a compou ...

s which provide a supplementary source of water in plants by reducing the surface tension of dew, allowing it to be absorbed more easily. Acylsugars are also used in pesticides, food additives, cosmetics and personal care products, antibiotics, and anti inflammatory medications. Therefore, acylsugars have been the focus of studies aiming to discover successful breeding crop techniques and synthetic methods of metabolizing acylsugars.

References

Secondary metabolites Acyl groups

Distribution

Functions

See also

References