REVIEW ARTICLES CURRENT SCIENCE, VOL. 111, NO. 8, 25 OCTOBER 2016 1325 *For correspondence. (e-mail: biok.anish@gmail.com) Methoxybenzaldehydes in plants: insight to the natural resources, isolation, application and biosynthesis Anish Kundu 1,2,3, * and Adinpunya Mitra 1 1 Natural Product Biotechnology Group, Agricultural and Food Engineering Department, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India 2 Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, SKS7N 5C9, Canada 3 Present address: National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi 110 067, India Methoxybenzaldehydes in plants are one of the impor- tant groups of benzoate derivatives. Some of them, exhibiting refreshing fragrance can be used as fla- vouring ingredients in food and cosmetics. Therefore, they have important roles in food and cosmetic indus- tries. Methoxybenzaldehydes also exhibit significant medicinal properties and thus have certain prospects in pharmaceutical industry. Biosynthesis of benzoic acid in plants has been explored in the last decade. There has been focus on benzaldehyde and methoxy- benzaldehyde biosynthesis as well. There have been several studies regarding the biosynthetic route and mechanism of formation of benzaldehyde via benzoic acid from cinnamate and further addition of ‘meth- oxy’ group to it in the last few years. Still there are many ambiguities regarding the medicinal properties and biosynthesis of methoxybenzaldehydes. This re- view highlights the latest advances in fragrant meth- oxybenzaldehyde research and the knowledge gaps till date. The review also discusses the occurrence of meth- oxybenzaldehydes in plants, their separation methods, medicinal properties and biosynthesis. Keywords: Biosynthesis, plants, medicinal properties, methoxybenzaldehyde, vanillin. BIOSYNTHESIS of benzoic acid and its derivatives has been in focus in the last few years, but methoxybenzalde- hyde biosynthesis remains a partially explored area 1 . Methoxybenzaldehydes generally have a characteristic fragrance and contain a single ‘methoxy’ group in the ortho, para or meta position of the benzene ring of ben- zaldehyde (Figure 1). They are regarded as natural prod- ucts of plants with medicinal and industrial importance 2,3 . For example, vanillin, a popular and widely used flavouring methoxybenzaldehyde was an area of interest for plant biologists in the last decade due to its direct usage in food and beverage industries. Its specific use as flavouring agent as well as preservative makes it industrially impor- tant. On the other hand, ambiguities of its biosynthetic route have not yet been fully explored. Vanillin is extracted mainly from the orchid Vanilla planifolia and, to a lesser extent, from Vanilla tahitienis and Vanilla pompona 4 . Another interesting methoxybenzaldehyde, 2- hydroxy-4-methoxybenzaldehyde (MBALD), is found mainly in the roots of plants belonging to the family Apocynaceae. The root extracts are also used as flavour- ing agent, mostly in the southern part of India, specially as food and drink ingredient 5,6 . MBALD was reported to exhibit medicinal properties such as anti-acetyle- cholinesterase, antityrosinase and antileukemic activi- ties 2,3,7,8 . There are many other plants which produce and accumulate different homologous methoxybenzaldehydes in different organs (Figure 1) and these have to be con- sidered for future research in this area. In brief, the im- portance of methoxybenzaldehydes in natural products research cannot be overlooked as they have functional and potential roles in medicine, agriculture and industry. Therefore, up-to-date knowledge is required for further progress in methoxybenzaldehyde research. In this article, we discuss the available scientific literature regard- ing the occurrence of methoxybenzaldehydes in plants as natural products, methods of separation, medicinal prop- erties and biosynthesis. Thus, we aim to compile informa- tion on the research in this field and review the latest advances in the fragrant methoxybenzaldehyde research. Occurrence of methoxybenzaldehydes in plants Accumulation of fragrant methoxybenzaldehydes in plant is reported mainly in roots, bark and pod, although there are examples of plants producing methoxybenzaldehydes in other organs like leaves and seeds. It has been reported that MBALD is the major chemical constituent (80%) found in the essential oils from root extract of Hemides- mus indicus 5 . Apart from H. indicus, Decalepis hamil- tonii has also been reported to accumulate MBALD in roots as a chief chemical constituent (96%) 9,10 (Table 1). Accumulation of MBALD was found to be enhanced after chitosan and yeast extract treatment in H. indicus field roots 1,11 . Enhanced accumulation of MBALD was