Myrtle leaves as well as the volatile oil (Myrtii Oleum) obtained from the leaves are used to lower the blood glucose level in type-2 diabetic patients in Turkish folk medicine. Myrtle extracts are very rich in polyphenols. In particular, galloyl-glucosides, ellagitannins, galloyl-quinic acids, flavonol glycosides and hydrolysable tannins (galloyl-glucosides, ellagitannins, galloyl-quinic acids).  They have a potent antioxidant activity mainly due to the presence of galloyl derivatives.

Benefit
Myrtle "Addus" (Myrtus communis) has long history as a traditional medicine or different infectious disease by many peoples of the world and in Africa, for instance Ethiopia.

Antioxidant
Myrtle (Myrtus communis), a culinary spice and flavoring agent for alcoholic beverages widespread in the Mediterranean area and especially in Sardinia, contains the structurally unique oligomeric non-prenylated acylphloroglucinols, semimyrtucommulone and myrtucommulone A that are strong antioxidants.

Myrtle Research
Inhibition of alpha-glucosidase by aqueous extracts of some potent antidiabetic medicinal herbs.
Prep Biochem Biotechnol 2005.
Biochemistry Department, Faculty of Science, Ege University, Bornova, Izmir, Turkey.
Diabetes mellitus is one of the most prevalant diseases of adults. Agents with alpha-glucosidase inhibitory activity have been useful as oral hypoglycemic drugs for the control of hyperglycemia in patients with type 2; noninsulin-dependent, diabetes mellitus (NIDDM). Investigation of some medicinal herbs: Urtica dioica (stinging nettle), Taraxacum officinale, Viscum album, and Myrtus communis ( myrtle ) with alpha-glucosidase inhibitor activity was conducted to identify a prophylactic effect for diabetes in vitro. All plants showed differing potent alpha-glucosidase inhibitory activity. However, myrtle strongly inhibited the enzyme. The inhibitory effect of these plants and some common antidiabetic drugs against the enzyme source (baker's yeast, rabbit liver, and small intestine) were also searched. Approximately all inhibitors used in this study showed quite different inhibitory activities, according to alpha-glucosidase origins. Furthermore, subsequent separation of the active material from myrtle by HPLC showed that only one fraction acted as an a-glucosidase inhibitor.

Hypoglycaemic effects of myrtle oil in normal and alloxan-diabetic rabbits.
J Ethnopharmacol. 2004.
Department of Biochemistry, Faculty of Medicine, Gazi University, Besevler, Ankara, Turkey.
However, little attention has been paid to the therapeutic use of this plant. The present study was designed to investigate the oral hypoglycaemic activity of single and multiple doses of myrtle oil in normal and alloxan-diabetic rabbits. The above observations show that myrtle oil exerts hypoglycaemic as well as mild hypotriglyceridemic activity in diabetic animals. The reduction in blood glucose level may be due to the reversible inhibition of alpha-glucosidases present in the brush-border of the small intestinal mucosa, higher rate of glycolysis as envisaged by the higher activity of glucokinase, as one of the key enzymes of glycolysis, and enhanced rate of glycogenesis as evidenced by the higher amount of liver glycogen present after MO administration.

Questions from readers
I am interested in learning what research has been done on the anti-inflammatory effects or other pain reducing effects of the herb, Myrtle. Perhaps it might be used in connection with fibromyalgia.
    I have not seen human studies on the role of this herb or extract in terms of treating fibromyalgia as of 2011.

Do you know if there is research on use of the herb in assisting with pain?
    Not that I am aware of.