Labdane-Type Diterpenes, Galangalditerpenes A–C, with Melanogenesis Inhibitory Activity from the Fruit of Alpinia galanga

Abstract

In our continuing study of biologically active natural products from the fruit of Alpinia galanga (Zingiberaceae), we newly isolated three new labdane-type diterpenes, termed galangalditerpenes A–C (1–3), along with four known sesquiterpenes (4–7) and two diterpenes (8 and 9). The stereostructures of 1–3 were elucidated on the basis of their spectroscopic properties. The melanogenesis inhibitory activities in theophylline-stimulated murine B16 melanoma 4A5 cells of these isolates, including the new diterpenes (1–3, IC50 = 4.4, 8.6, and 4.6 μM, respectively), were found to be more than 6–87-fold higher than that of arbutin (174 μM), a commercially available positive control.

Antimycobacterial Activity and Safety Profile Assessment of Alpinia galanga and Tinospora cordifolia

“…Our phytochemical screening showed the presence of terpenoids, essential oils, phenolic compounds (phenylpropanoids), and flavonoids in A. galanga . These results are in agreement with data reported on the chemistry of A. galanga [ 34 – 37 ]. Moreover, our data revealed the presence of terpenoids, alkaloids, and flavonoids in T. cordifolia .…”

Geranylated Coumarins From Thai Medicinal Plant Mammea siamensis With Testosterone 5α-Reductase Inhibitory Activity

“…In particular, many heterocyclic compounds based on oxygen and nitrogen atoms often have good antiproliferative activity against a variety of solid tumor cell lines and are expected to be seeds of new anticancer agents (Sharma et al, 2018;Petel et al, 2019). During our characterization studies on bioactive constituents from Thai natural medicines (Manse et al, 2017;Morikawa et al, 2018;Tanabe et al, 2018;Kobayashi et al, 2019), a methanol extract of the flowers of M. siamensis was found to inhibit 5αreductase activity (IC 50 = 2.4 µg/mL). In order to investigate new 5α-reductase inhibitors, we conducted a search for the bioactive constituents from the flowers of M. siamensis.…”

Structural Requirements of Alkylglyceryl-l-Ascorbic Acid Derivatives for Melanogenesis Inhibitory Activity

“…Effects on melanogenesis in NHEMs were examined according to a protocol described previously [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 34 ] with modifications. The cells (3.0 × 10 5 cells/2 mL/well) were seeded into 6-well multiplates.…”

“…Tyrosinase activities using l -tyrosine or l -DOPA as a substrate were determined according to the protocols described previously [ 20 , 22 , 23 , 24 , 25 , 26 , 27 ]. Briefly, samples, l -tyrosine (2.5 mM, or l -DOPA, 3.0 mM), mushroom tyrosinase (46 units/mL), and phosphate buffer were mixed in a 96-well plate and incubated at 25 °C.…”

“…In our previous investigation of compounds from several natural resources possessing melanogenesis inhibitory activity, we reported that dimeric pyrrolidinoindoline- [ 20 ], aporphine- [ 21 , 22 ], benzylisoquinoline- [ 22 ], and phenanthridine-type [ 23 ] alkaloids, as well as phenylethanoid glycosides [ 23 ], methoxyflavones [ 24 ], phenylpropanoids [ 25 ], neolignans [ 25 ], and diterpenes [ 26 , 27 ] exhibited significant positive effects against theophylline-stimulated melanogenesis in B16 melanoma 4A5 cells. As a continuing study on melanogenesis inhibitors from naturally occurring compounds and their related analogs, we focus on l - ascorbic acid (AsA), one of the most recognized sugar acids, and its highly stable derivatives.…”